Volume 21, Issue 7

A Lorenz-invariant treatment of the second order DOPPLER effect in rotational motions is given. The calculation is then performed in a generally covariant manner. Experimental consequences concerning the mechanical stability of clocks are discussed, and attention is drawn to a possible refinement of the rotational experiments.

In this paper we discuss the influence of the PAULI principle on some properties of nuclear systems consisting of a cluster surrounded by many other nucleons; to do this we use two models. We find that, though transition probabilities may be influenced drastically, the general features of the energetical behaviour of such systems is practically unaffected by the exclusion principle. The consequences for real nuclei are discussed: For instance, closed shells remain energetically favoured even if surrounded by many other nucleons.

We here develop a formalism of nuclear fluctuation theory which we hope makes transparant the general structure of nuclear fluctuation theory and allows us to draw conclusions on the statistical properties of any kind of intensity which can be observed from a nuclear reaction. In the present paper the discussion concentrates on the case of compound reactions of purely fluctuating nature.

The phenomenon of the distribution of a doorway state over many complicated compound nuclear states, i. e. the formation and properties of a so-called micro-giant resonance, are investigated analytically and numerically by means of a simple model. The distribution of the poles in the complex plane and the distribution of the residues of the S-matrix are obtained numerically and used to calculate the average cross-section. It is shown that the LANE-THOMAS-WIGNER theory applies, except for a possible correction to the shape of the resonance occuring in the cross-section averaged over the energy. This shape need not be describable by a LORENTzian. Estimates of the “spreading width” W and the “total width” W 0 are given for particular cases. It is noteworthy that the relationship W 0 =W+Γ need not be correct even as an order-of-magnitude estimate, where Γ is the decay width of the doorway state.

Directionality of alpha emission in terms of alpha-alpha angular correlation distributions between the consecutive alpha particles in the serial decay of Th 228 is experimentally studied from Thorium stars produced in emulsion plate. The angular correlations fit a sin Θ-distribution.

Previously unreported decay characteristics of 51 Sc are studied. The activity was obtained from a series of bombardments of an enriched 48Ca target (in the carbonate form) with 18 MeV α particles, β ray measurement of the investigated sample indicated a component of ~ 5 MeV endpoint energy which decays with a half life of 12 sec. γ ray measurements gave new lines at 1.44 MeV and 2.16 MeV, both decaying with a half life of ~ 12 sec. The γ-ray energies coincide with some of the energies of the states observed in 51 Ti from the 50 Ti (d, p) reaction and the β endpoint energy is in agreement with the known Q value of the 48 Ca (α, p) 51 Sc reaction. All decay characteristics are quite consistent with theoretical predictions.

The βv- and βα-angular correlations for the decay of 8 Li→ 8 Be*→2α previously studied have been remeasured with an improved experimental setup. In addition we have measured these correlations for the decay 8 B→ 8 Be→2 α. For the coefficient b in the angular correlation between β-, ν- and α-particle for Gamow—Teller interaction W (b,,ϑ,φ)dΩ=[1+bv/c) cos ϑ·cos φ] dΩ we got b( 8 Li) = —1,01 ± 0,07 and b ( 8 B) =1,05 ± 0,12. Both results are in agreement with pure axial vector interaction. For the coefficient B in the angular correlation between β- and α-particle W(Θ) dΩ= (1+A·cos Θ+B·cos 2 Θ) dΩ we got B ( 8 Li) = (+0.0031 ± 0.0003) · W β and B ( 8 B) = (-0.0023 ±0.0003) ·W β . The experimental result δ=B ( 8 Li) —B ( 8 B) = (0.0054 ± 0.0004) W β is within the range predicted by the Conserved Vector Current theory.

Many experiments indicate that isospin is not a good quantum number for the states with J π=2 + at 16.6 MeV and 16.9 MeV in Be 8 . The available experimental information is examined and compared with a model of single particle states which are maximally mixed in isospin, as proposed by MARION. An analysis of all data pertinent to the states at 17.6 MeV and 18.15 MeV with J π=1 + shows that these states are rather pure (90%) isospin states. The state at 17.6 MeV has T=1, the one at 18.15 MeV hat T=0. Both the 2 + and the 1 + levels form doublets with similar wave functions in each case. A similar pair is most likely formed by the 3* states at 19.05 MeV and 19.22 MeV, as proposed by BARKER. Reduced widths indicate possible isospin mixing of as much as 30% for these states. Some experimental evidence is presented for another pair of states with J π=1 - at 20.35 MeV and 22 MeV, and with J π=2 - at 18.9 MeV and 23.6 MeV. This hypothesis provides analog states in Be 8 for every state observed in Li 8 in the energy region which is considered. If each pair (except the 1 + and 2 + pairs) is allowed to mix isospin by at most 30%, all cases of large excess of either neutron or proton reduced width can be explained. The large isospin mixture in the 2* pair can be explained on the basis of an initial energy degeneracy of these states (removed by the COULOMB force). The intermediate coupling shell model does account for such an accident. It is argued that, although a simple cluster picture of these states is highly successful in a qualitative way, the intermediate coupling model is able and probably needed to achieve a quantitative description of Be 8 between 16 and 20 MeV.

Excitation functions for the elastic proton scattering from the target nucleus 144 Sm have been measured in the energy-range from 8.600 to 11.600 MeV at six different scattering angles. Strong resonances were observed in the highly excited compound nucleus 145 Eu, which are the isobaric analogues to the low-lying states of 145 Sm. The resonances have been interpreted as BREIT-WIGNER resonances, superimposed on a smoothly varying background. The analysis was carried out in terms of a single level approximation. Energies, l-values, and widths of these resonances have been determined, and are compared with corresponding results of (d, p) -experiments.

The systematics of M1 and E2 transition probabilities between low lying states in odd A rotational nuclei are reviewed. Some departures are found from strict rotational behaviour in ratios of M1 and E2 transition probabilities in successive transitions.

MÖSSBAUER experiments have been performed on the 88.3 keV level in Hf 176 and the 93.3 keV level in Hf 180 . A model-independent ratio for the quadrupole moments of the 2 + rotational states could be derived from the measured hyperfine splittings. The result is Q(Hf 176 ) / Q (Hf 180 ) =1.10 ±0.02 in agreement with the model-dependent value calculated from the transition probabilities.

The elastic scattering of 14 N on 9 Be at 25 MeV and 16 Ο on 11 B at 30 MeV has been measured and analyzed with Optical Model and Ingoing Wave Boundary Condition calculations. Acceptable fits were obtained for the angular region below 100° c.m. The reflection coefficients derived from these calculations are compared with the Diffraction Model calculations of DAR to the corresponding p- and α-transfer reactions, in which a WOODS-SAXON distribution of the reflection coefficients is used.

Excitation functions of proton elastic scattering on the even-even nuclei Cr 54 and Fe 56 have been measured at incident proton energies from 9.3 to 10.11 MeV in 5 keV steps and from 9.27 to 9.57 MeV in 2 keV steps respectively and from 11.5 to 11.9 MeV in 5 keV steps for Fe (p,p 0 ) only. Seven silicon surface barrier detectors were used to get angular distributions from 63° to 173°. The observed cross-section fluctuations are interpreted in terms of ERICSON'S statistical theory. From the strength of the fluctuations differential compound elastic cross-sections are deduced. The results are compared with HAUSER-FESHBACH calculations and are generally discussed with respect to the optical model.

Angular distributions for elastic and 2 + inelastic deuteron scattering from Mg 24 have been obtained at various energies in the range from 6 to 13 MeV. Yield functions have been measured in 50 keV steps at 90° and 150°. In the region from 10 to 13 MeV, the elastic angular distributions show an anomalous behavior : instead of moving in from 180°, a new maximum is created by the breakup of a broad maximum at about 100° into two maxima. The inelastic angular distributions do not show such an anomalous energy dependence. Therefore the Blair phase rule between the elastic and the 2 + inelastic angular distributions breaks down in the energy region of the anomaly in the elastic scattering, but it holds outside this energy region. In spite of fluctuations in the excitation functions, an optical-model analysis of the elastic angular distributions yields parameters which, with the exception of W, vary smoothly with energy.

Some regularities in the experimental angular distributions of inelastically scattered deuterons (E d ∼ 11.8 MeV) corresponding to the lowest 2 + states of the even nuclei 12 C, 20 Ne, 22 Ne, 24 Mg, 26 Mg, 28 Si, 32 S, 40 A, Ti, 52 Cr, Fe, 58 Ni, Zn, Kr, Sr and Zr are discussed. BLAIR’S phase rule is approximately valid for strongly deformed nuclei in the region of 24 Mg, whereas it is not valid for the other nuclei. The latter also results from DWBA calculations which have been carried out for nuclei with mass number A ≧ 40, using a real coupling potential. Several different sets of optical parameters have been used for the calculations and it is found that the extracted deformation parameters depend considerably on the choice of the optical potential.

The nuclear reactions of 52 MeV deuterons have been studied at some medium weight and heavy nuclei. The angular distributions of elastically scattered deuterons show sharp structures which are smoothed out — similar to the results at lower deuteron energies — for target nuclei near A = 100. The optical model analysis gives good fits with parameters extrapolated from the best values at lower energies. The „Smoothed Cut-off“ models do not describe the results properly. The influence of the nuclear interior on the elastic scattering is important. The proton spectra from the (d, p) and (d, pn) reactions are dominated by a broad „break up“ maximum. From the width of the maximum and the A-dependence of the cross section it is concluded that nuclear break up is more frequent at 52 MeV than COULOMB break up. The spectra of deuterons and tritons from the (d, d′) and (d, t) reactions show maxima up to Q-values of — 15 MeV. With these reactions it should be possible to study collective excitation up to high excitation energies and to get information about inner shells. The intensity of low energy inelastic deuterons is surprisingly large.

Winkelverteilungen der Reaktion N 14 (d, α) C 12 wurden im Energiebereich 0,5 bis 2,2 MeV bei neun verschiedenen Deuteronenenergien gemessen. Die gewonnenen Meßwerte wurden durch LEGENDRE-Polynome approximiert. Die Analyse weist auf die Existenz von mindestens 3 Niveaus hin.

Es wurden die Reaktionen 30 Si(d, p) 31 Si bei Ed = 10 MeV und 30 Si( 3 He, d) 31 P bei E 3 He = 15 MeV mit einem Breitbandmagnetspektrographen untersucht. Für 31 Si wurden Winkelverteilungen für 20 Niveaus von 5° bis 120° gemessen und mit einer DWBA Analyse wurden l-Werte und spektroskopische Faktoren bestimmt. Auf Grund der Targetzusammensetzung wurden zugleich mit dem 31 Si 23 Niveaus im 29 Si gemessen, deren spektroskopische Faktoren mit früheren Messungen 1 übereinstimmen. Die l = 2 Winkelverteilungen sind strukturiert oder flach je nach dem dem Spin 3/2 + oder 5/2+ des Endzustandes, so daß sich durch Vergleich auch die Spins der Niveaus im 31 Si bestimmen ließen. Im 31 P wurden die l-Werte und relativen spektroskopischen Faktoren aus 4 Spektren bei 4 ausgewählten Winkeln bestimmt. Eine Interpretation der Niveaustruktur und der spektroskopischen Faktoren von 31 Si und 31 P nach den Schalenmodellrechnungen von GLAUDEMANS et al. 2 schlägt fehl, vor allem da in den Rechnungen die d 5/2 Schale als abgeschlossen betrachtet wird. Die versuchsweise Anwendung des NILssoN-Models führt auf kleine Deformationen | η | < 2, ohne die Niveauleiter indessen exakt erklären zu können.

In der Kernniveaudichte nach dem FERMI-Gas-Modell wird die Abhängigkeit der Dichte der Kernniveaus vom Drehimpuls des Kerns wesentlich durch den Spinabschneideparameter σ bestimmt. Dieser kann unter anderem aus den Winkelverteilungen der emittierten Teilchen und aus dem Verhältnis isomerer Wirkungsquerschnitte für Compoundkernreaktionen erhalten werden, die sich nach der statistischen Theorie der Kernreaktionen beschreiben lassen. Für einige Kernreaktionen schneller Neutronen wurden derartige Meßdaten ermittelt und daraus Spinabschneideparameter σ für die Kerne Ar 37 , Co 58 , Ni 61 , Ge 75 und Se 73 abgeleitet. Die Ergebnisse werden verglichen mit entsprechenden Angaben anderer Arbeiten für mittelschwere Kerne und mit den Voraussagen des FERMI-Gas-Modells.

Fissionability, mass distribution, charge dispersion and distribution, and neutron emission for fission induced in heavy targets (uranium) by protons with a few hundred MeV kinetic energy are presented and phenomenologically discussed. The results are interpreted in order to arrive at the reaction mechanisms in medium high energy induced fission.

The reactions 26 Mg (p, α) 23 Na, 37 Cl(p, α) 34 S, and 45 Sc (p, α) 42 Ca have been studied. Excitation functions and angular distributions were measured for proton energies 9 to 13.26 MeV, 11 to 11.952 MeV, and 8.5 to 9.412 MeV in steps of 20 keV, 8 keV, and 6 keV, and the transitions into 4, 3, and 5 final states have been resolved, respectively. All the excitation functions exhibit strong fluctuations and were analysed in terms of the various correlation functions, from which the mean level width Γ, the normalised variance, and the amount of direct interaction contribution was derived. Statistical model calculations have been used to fit the averaged angular distributions and an attempt was made to estimate the J-dependence of the mean level width Γ in the compound nuclei excited at about 20 MeV.

The differential cross sections of the 208 Pb(d, p) 209 Pb transitions to the states 9/2 + , 5/2 + *, ½ + , 7/2 + , and 3/2 + in 209 Pb were measured at 135° laboratory angle for deuteron energies between 7.0 and 10.5 MeV. The data below 8.0 MeV were analyzed in COULOMB Wave BORN Approximation to give accurate spectroscopic factors of the five levels according to a simple shell model potential in the final nucleus. The dependence on some of the parameters that determine this potential is studied. The absolute value of the normalizing constants of the bound neutron wave functions outside the nuclear potential well are determined without reference to any shell model potential, i. e. their true values are given. It is confirmed that the ground and excited states up to 2.52 MeV in 209 Pb are pure single particle states so that from their study one can draw a proper shell model potential in the lead region.

The cluster model of nuclear fission makes definite predictions about the charge distributions. The assumptions made in the computation of mass distributions have to be supplemented by the postulate of statistical sharing of the surplus protons and neutrons between light and heavy cluster. Given the mass distributions, the charge distributions are completely determined by statistical considerations. The calculated average charge 〈Z P 〉 as a function of fragment mass number Ap for thermal neutron induced fission of U 235 agrees rather well with the radiochemical results and some recent mass spectroscopic measurements. The shape of the charge distribution around 〈Zp〉 depends on Ap , and is in fair agreement with the available data.

Available experimental spallation data have been used to construct a five-parameter formula describing the cross-section distribution for a wide range of experimental conditions with a fair degree of accuracy. The application of the cross-section formula to different fields of research is indicated.

The reactions leading to the production of 11 C from 12 C and 27 Al, and of 18 F from 27 Al were studied with antiprotons and negative pions of momentum (2.5—3.0)GeV/c. No significant differences were found in the cross-section ratios. The experimental uncertainties are in the order of 25%.

Für die Molekülgase Wasserstoff, Ammoniak, Kohlendioxid, Luft und Acetylen, sowie für Wasserdampf und Äthanoldampf wurden die Wirkungsquerschnitte o 1-1 für den Umladeprozeß He + He - gemessen und die Abhängigkeit des Wirkungsquerschnittes von der Energie der Primärionen (15 bis 72 keV) untersucht. Für die genannten Gase und Dämpfe wurde ferner die maximale Ausbeute an negativen Heliumionen in Abhängigkeit von der Energie der Primärteilchen bestimmt. Die maximalen Wirkungsquerschnitte liegen für die benutzten Gase und Dämpfe bei 0,6·10 -19 cm 2 . Der Verlauf von σ 1-1 als Funktion der Energie der He + -Ionen ist für die meisten der untersuchten Molekülgase komplizierter als für Edelgase als Targetmedien. Der maximale Anteil der negativen Heliumionen am Gesamtstrom betrug bei der Umladung in Luft 0,11‰, in Äthanoldampf 0,11‰, in Wasserdampf 0,13‰, in Ammoniak 0,14‰, in Wasserstoff 0,15‰, in Acetylen 0,19‰, und in Kohlendioxid 0,20‰.

Energy losses of B-, N-, O- and S-Ions in gold-, silver- and nickel-targets were measured by a new method, based on the elastic backward scattering of these ions from thick targets. The agreement of the results with semiempiric estimates of Northcliffe is excellent as far as these estimates are made. Charge distributions of O- and S-Ions after scattering from thick targets were also measured and the values of γ 2 determined. The energy losses calculated from these γ 2 values agree within the errors with the directly measured values.

Durch Messung der Leitfähigkeit und des Hall-Effekts wurde die Abnahme der Konzentration und der Beweglichkeit der Ladungsträger in n- und p-GaAs bei Bestrahlung mit 3 MeV-Protonen untersucht. Gemessen wurde die Abhängigkeit von der Bestrahlungsdosis und von der Ausgangsdotierung (n 0 =5 · 10 15 — 3 · 10 18 cm -3 , p 0 = 2 · 10 17 – 8 · 10 18 cm -3 ). Die Träger-Vernichtungsrate erweist sich dabei als stark abhängig von der Lage des Fermi-Niveaus und von der Vorbestrahlung. Die kleinsten noch meßbaren Trägerkonzentrationen lagen bei n ≈ 10 9 cm -3 und p ≈ 10 10 cm -3 , entsprechend einer Leitfähigkeit von 10 -7 Ω -1 cm -1 . Diese Meßgrenze wird offenbar durch leitende Oberflächenschichten bestimmt. Die Extrapolation der Meßergebnisse läßt aber erwarten, daß bei fortgesetzter Bestrahlung die Trägerkonzentration von p-GaAs (Cd dotiert) sich einem Grenzwert p* ≈ 1 · 10 9 cm -3 nähert und daß n-GaAs zu p-GaAs konvertiert und denselben Grenzwert erreicht (E F * E V +0,58 eV). Die Elektronenbeweglichkeit nimmt bei Bestrahlung monoton ab bis ca. 10 -2 des Ausgangswertes. Die Löcherbeweglichkeit durchläuft dagegen ein Minimum. Wie die Analyse der Ergebnisse zeigt, müssen durch Bestrahlung in GaAs sowohl Donatoren als auch Akzeptoren erzeugt werden, und zwar in einer innerhalb etwa 0,1 eV quasikontinuierlichen Verteilung, wobei diese Verteilung jeweils von der nächstgelegenen Bandkante bis zu einem Abstand von mindestens 0,50 eV von dieser reicht.

Es wurde der Formierungsvorgang von Oberflächensperrschichten auf goldbedampftem n-Silicium untersucht, wobei Goldschichtdicke, Temperatur und Sauerstoffdruck variiert wurden. Gemessen wurde in allen Fällen die Verzögerungszeit, die zwischen dem Zeitpunkt der Sauerstoffzufuhr und der Ausbildung der Sperrschicht liegt. Die Aktivierungsenergie der Sauerstoffdiffusion beträgt 0,85 ± 0,04 eV. Die Verzögerungszeit ist quadratisch von der Goldschichtdicke abhängig und zeigt weiterhin eine Druckabhängigkeit.

The scintillation light yield S of three anorganic [NaJ (Tl), KJ (Tl), CsJ (Tl)], of two organic (p-terphenyl, anthracene) crystals, and of plastic NE 102 by bombardement with deuterons in the energy range from 10,0—27,5 MeV, α-particles from 8,0—55,0 MeV, and electrons has been measured. The time constants of the electronic circuit have been chosen to τ 1 = 0,5 sec and τ 2 = 2,0 µsec. The pulse-height ratios S D /S β and S α /S β are slightly different for the two time constants. The anorganic crystals have a higher pulse-height ratio for the short time constant, whereas the organic crystals and plastic show the inverse effect.

Die durch Röntgen-Strahlen erregte Fluoreszenz wäßriger Farbstofflösungen zeigt bei Zusatz von löschenden, selbst nicht fluoreszierenden Substanzen ein gänzlich anderes Verhalten als ihre durch UV erregte Fluoreszenz. Es ist wahrscheinlich, daß ein wesentlicher Teil der Fluoreszenz durch Vereinigung von hydratisierten Elektronen und positiven Farbstoffionen zustande kommt.

Un plasme confiné par une configuration polyédrique est exploré au moyen d’une sonde piézoélectrique et photographié avec une caméra électronique. La configuration de champ est formée de deux systèmes de conducteurs, l’un octaédrique et l’autre cubique tronqué, alimentés par des courants de haute fréquence déphasés de 90° l’un par rapport à l’autre. Le tout se comporte en moyenne comme un cusp possédant un grand nombre de points de fuite répartis sur une sphère. On observe une onde sphérique convergente. Le rendement du transfert d’énergie au plasma est élevé.

In den letzten Jahren sind bei der Erzeugung von dichten und heißen Plasmen mit den sog. linearen Theta-Pinch-Apparaturen große Fortschritte erzielt worden. Die Einschlußzeiten bleiben jedoch begrenzt auf einige Mikrosekunden, da bei den linearen Apparaturen das Plasma entlang der Feldlinien an den Enden der Spule ausströmen kann. Daher wurden Untersuchungen an toroidalen Theta-Pinchen durchgeführt, die hier zusammenfassend dargestellt werden. Im rein kreisförmigen toroidalen Magnetfeld driftet das Plasma in Richtung wachsenden Radius des Torus, ist also nicht im Gleichgewicht. Mit zwei speziellen toroidalen Feldkonfigurationen, dem sog. M+S und dem toroidalen Theta-Pinch mit überlagertem Hexapolfeld, konnte experimentell ein Gleichgewicht angenähert bzw. erreicht werden. Die M+S-Konfiguration gehört zur Klasse der geschlossenen Konfigurationen, bei denen besonders die Stabilitätsfrage untersucht wird. Der toroidale Theta-Pinch mit überlagertem Hexapol gehört zur Klasse der offenen Konfigurationen. Er zeigt in Übereinstimmung mit den theoretischen Erwartungen ein stabiles Verhalten. Die sog. Cusp-Verluste an den offenen Stellen dieser Konfiguration wurden experimentell bestimmt und mit den Verlusten verglichen die aus verschiedenen Modellen folgen. Die theoretischen Erwartungen lassen für die Verlustraten einen Spielraum von zwei Größenordnungen. Die vorläufigen experimentellen Ergebnisse deuten auf die theoretisch günstigeren Möglichkeiten hin.

The propagation of waves in the solar atmosphere is investigated with respect to the problem of the chromospheric spiculae and of the heating of the solar chromosphere and corona. In particular the influence of external magnetic fields is considered. Waves of finite amplitudes are numerically calculated by solving the time-dependent magnetohydrodynamic equation for two spatial dimensions by assuming axial symmetry. For the case without a magnetic field the comparison between one dimensional and two dimensional treatment shows the strong influence of the radial propagation on the steepening of waves in the vertical direction. In the presence of a magnetic field it is shown that the propagation is strongly guided along the lines of force. The steepening of the waves along the field is much larger as compared to the case where no field is present.

The observations of the Lithium abundance and the isotope ratio Li 6 /Li 7 in stars are briefly reviewed and some simple conclusions are drawn. It is emphasized that — in addition to the mechanism proposed by BODENHEIMER — a slow (timescale ≈ 10 9 years) mixing process in main sequence F and G stars is necessary to account for the observations. The present state of the theory of convective overshooting is reviewed in this context. Two new models of the outer solar convection zone are presented. The temperature at their lower boundaries are 2.04 x 10 6 °K and 2.27 x 10 6 °K, showing that only a rather small convective overshoot may be sufficient for mixing the matter in the convection zone with the layers, in which Li 7 is burnt. Our models differ from earlier ones, because (when calculating the mean stratification) we take into account the condition that the mixing length can nowhere be larger than the distance from the nearest boundary of the convection zone. It is shown that this approach also leads to a slight change of the numerical factors in the formulae usually used.

The question if submicron particles could be present in interplanetary space is discussed in some detail. On the assumption that the polarization of the zodiacal light is due to scattering of sunlight by submicron particles their spatial density is derived (chapter 2). The investigation of the forces exerted on those particles by the radiation pressure of sunlight and by interaction with the particles and magnetic fields of the solar wind shows that the „lifetime“ of submicron particles in interplanetary space is probably less than 10 3 years (chapter 1 and 3). Therefore it seems doubtful that they can exist in considerable numbers.

Aus der Beobachtung der von der kosmischen Strahlung erzeugten Isotope Be 7 , P 32 , P 33 und S 35 sind Rückschlüsse auf die Geschichte einer Luftmasse möglich. Messungen der Absolutkonzentrationen und der Isotopenverhältnisse an Regenwasserproben im Jahre 1965 zeigen, daß sich der Einschub stratosphärischer Luft in die Troposphäre im Einzelfall nachweisen läßt. Die Bestimmungen des P 33 -Gehaltes deuten darauf hin, daß der in der Literatur benutzte Ausbeutefaktor um etwa 25% zu klein angesetzt ist.

Das radioaktive Aerosol der atmosphärischen Luft wird nach dem Filterverfahren abgeschieden. Während der Durchsaugung wird die gesamte β-Strahlung, die α-Strahlung von RaA und RaC' und die des ThC′ getrennt gemessen. Das konstante α/β-Verhältnis der Zerfallsraten der natürlichen Strahler wird benutzt, um die von Spaltprodukten herrührende β-Aktivität direkt zu bestimmen.

Co 60 and Ar 39 were measured in a number of recently fallen meteorites. From these data the amount of shielding surrounding the samples in space was estimated. In the carbonaceous chondrite, Murray, the Co 60 activity was very large compared to the Co 60 activities in the other chondrites even though the Ar 39 activities were almost identical. In the iron meteorites there was an inverse relationship between the Co 60 and Ar 39 activities; shielding material increased the Co 60 activity and decreased the Ar 39 activity. In the cases of Abee and Bruderheim, neutron exposure ages were obtained from the Kr 80 /Co 80 , Kr 82 /Co 60 , and Xe 128 /Co 60 ratios because the Co 60 was measured in large samples from the interior of the same fragment in which krypton, xenon, bromine, and iodine had previously been measured. The neutron exposure ages were approximately an order of magnitude larger than the spallation exposure ages. The order-of-magnitude differences in the exposure ages could be attributed to space erosion or to an ancient neutron irradiation.

Rare gas measurements (helium and neon) were carried out on single mineral components of 10 bronzite-chondrites, 10 hypersthene-chondrites and 1 amphoterite. Diffusion losses of 3 He were detected in pyroxene on most meteorites studied. The helium content of olivine was found to be far less effected by diffusion compared to pyroxene. A loss of spallogenic helium is always connected with a loss of radiogenic helium. For most of the bronzite-chondrites the loss of radiogenic helium occured only during the time of cosmic ray exposure due to a more intensive heating caused by orbits closer to the sun. Bronzitechondrites containing high amounts of primordial gases showed equal relative losses of spallogenic and radiogenic helium each. The reason for this unexpected results is not clear, but it might be that it results from a grain-size-effect and perhaps also holds true for all other meteorites as far as diffusion loss in space due to solar heating is concerned. Many of hypersthene-chondrites suffered inside their parent bodies considerable losses of radiogenic helium before their exposure to the cosmic rays. From the radiogenic helium content in pyroxene we calculated an age of 560 · 10 6 years for five of these meteorites, but we are not quite sure that this is a true age. It could be proved that the highly varying ratio of 3 He/ 21 Ne in chondrites cannot be attributed to diffusion losses. Variations up to a factor of 4 were confirmed. The content of 3 He in the metal phase of most meteorites investigated was found to be too low up to a factor of 2. A tritium loss in space is suggested as explanation of these deficiencies.

The argon and potassium contents of eight fluorite samples with microinclusions from the Schwarzwald, Germany, were measured by isotope dilution technique. The samples contain .5 to 5 × 10 -7 cc radiogenic Ar/g and there exists an approximate proportionality between the radiogenic and atmospheric argon component. In six samples the ratio Ar (rad) /Ar (total) at the time of mineral formation lies between .38 and .52 and probably represents the ratio in the mineral forming brine. These numbers are compatible with the argon ratios found in natural gases from bedrocks. ELINSON and POLYKOVSKII claim argon contents in fluid inclusions of pegmatitic feldspar ten times higher than the radioactive decay of K 40 in the lattice would produce. Assuming this excess occuring frequently in pegmatitic feldspar and the pertinent ε 0 -values > 0, there could be a considerable source of error for K-Ar-determinations of such minerals.

The isotopic composition of lead in archaeological objects can be used to trace the origin of this lead. In this paper we give the lead isotopic composition of 10 Roman lead pipes and ingots, found on the European continent. In spite of the limited number of samples and the restricted area, significant differences in the isotopic composition are found exceeding by far the experimental limits of error. Thus, it is shown that the isotopic composition of lead is indeed a sensitive tracer for the origin of historical lead objects. Our results are compared with the isotopic compositions of European lead ores. For some examples the possibilities and the limitations of the method are discussed.

Comparison of the radiocarbon content of a series of samples of dendrochronologically dated bristlecone pine wood with that from trees for which a so-called floating tree-ring chronology has been established makes it possible to determine an empirical age for this floating tree-ring series based upon the age of the wood used for comparison. For the case of the Swiss Lake Dwellers, the difference between conventional radiocarbon dates and the age values determined in this manner amounts to about 800 years. The age of the floating chronology was determined within a standard error of less than 40 years. The measurements indicate that the dwellings were constructed during the 38th century B. C.

Die vorliegende Arbeit beschreibt die Herstellung hochauflösender Ge (Li) -Detektoren nach verschiedenen Driftmethoden und den Entwurf eines schnellen Vorverstärkers mit einem Feldeffekt-Transistor in der Eingangsstufe. Die γ-Strahlung von 60 Co wurde mit 3 keV HWB aufgelöst. Für den Fano-Faktor ergab sich ein Wert von 0,20-0,25 im Energiebereich von 300-2750 keV.

Es wird eine Methode beschrieben, die es gestattet, für Konversionselektronen ν/c-Werte bzw. Impulse in Einheiten von m c absolut zu bestimmen. Dazu ist es nur notwendig, die Impulsverhältnisse von vier geeigneten Konversionslinien, die zu zwei parallel verlaufenden γ-Kaskaden gehören, mit hoher Genauigkeit zu messen. Die Methode wird auf Messungen des Zerfalls Ir 192 → Pt 192 angewandt und mit Ergebnissen verglichen, die auf anderen Eichverfahren beruhen. Außerdem werden RÖNTGEN-Termdifferenzen des Pt 192 in Einheiten von m c 2 abgeleitet und mit den Angaben der Literatur verglichen. Weiterhin eröffnet sich bei Hinzunahme von Daten über Spektrometergeometrie und Strommessungen eine neue Möglichkeit zur Bestimmung der spezifischen Ladung e/m des Elektrons. Es ergibt sich der Wert e/m = (1,7594 ± 0,0004) · 10 7 emE. Diese Genauigkeit entspricht jener der besten bisherigen Einzelmessung.

A spark chamber is described, for use of particle-path location in a magnetic spectrometer. The spark is localized electronically by inducing pulses in wire windings with co-ordinate-depending amplitudes. The method was proved in a spark chamber with 15 × 15 cm 2 electrodes of stainless steel meshes, with 13 wires per mm, 0.036 mm thick. A nearly linear slope for the calibration curve has been obtained with artificial sparks. Sparks at the same spot gave a pulse-height distribution with a half-width corresponding to 0.2—0.3 mm and a total spread of 0.4—0.7 mm. Results obtained with a Ce 144 β source showed, that a similar behaviour can be expected for natural sparks. This method renders possible a simple and compact set-up, without any restriction in respect to the material used for the electrodes of the chamber.