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The magnitude of isotopic changes induced in cosmic dust, due to nuclear interactions of solar and galactic cosmic rays, is calculated for several radioisotopes which seem suitable as signatures of cosmic dust in terrestrial environments. The rates of accretion of these radioisotopes depend on the composition and size distribution of cosmic dust, in addition to the cosmic dust mass influx rate, and the flux of low-energy particle radiation in space. The monitor radioisotopes are produced efficiently only in dust grains of certain preatmospheric size intervals; that is discussed separately for the monitor radioisotopes considered.

The self-diffusion of chloride ions in the bulk of nickel dichloride crystallites was studied in the temperature range of 180–340°C in a carefully-evacuated vacuum system; the isotopic exchange reaction between gaseous chlorine and the crystallites was also studied. The activation energy for the migration of chloride ions was determined to be 1.01 eV (=23.3 kcal/mol). The exchange reaction proceeded with activation energies of 3.6 and 9 kcal/mol for the active and the less-active part of the surface first layer, 13 and 16 kcal/mol for the active and the less-active one of the second layer, and 21 kcal/mol for the third layer. (These activation energies converge to the value of the self-diffusion in the bulk.) The Θ-rule nearly holds good in the present case.

The relative production ratio of 39Ar/36Cl in iron by 6.2 Bev protons has been measured to be 0.96 ± 0.05. This ratio is compared to the 39Ar/36Cl ratio of 0.98 ± 0.05 found in iron meteorites whose date of fall to the earth is known. It is concluded that the ratio of the average cosmic ray intensity during the last 300 years has been 1.02 ± 0.07 times the average cosmic ray intensity during the last 300,000 years. In this sense, cosmic ray intensity has been essentially unchanged.

The isotopic halogen exchange between POCl/sub 3/ and BCl/sub 3/ was investigated with the use of Cl/sup 36/ labeled reactants. While a rapid (complete within one minute) exchange is noted at O deg when POCl/sub 3/ is present in excess, as well as in an equimolar mixture of the two components, no halogen exchange is observed in an excess of BCl/sub 3/. These data are interpreted on the. basis of a structure previously proposed for the addition compound in which the bonding is through the phosphoryl oxygen. A mechanism for the rapid halogen exchange in POCl/sub 3/ rich systems is suggested, which does not necessitate the formation of a free tetrachloroborate anion as proposed in earlier studies of halogen exchanges in BCl/sub 3/.

Thermal activation, thermal absorption, resonance scattering, resonance transmission, and multiplicity of capture $\ensuremath{\gamma}$ rays have been measured for the stable isotopes of hafnium. Isotopic assignments of the various resonance levels are presented which are consistent with all the data observed. Where possible, the level spacing is estimated.

The radioactivities Be10, Al26, Cl36, Mn53, Ni59, and Co60 and the rare gas isotopes were measured in a sample taken from the surface of the Hoba meteorite. The spallation-produced radioactivities indicate that the sample was at a depth of 35 to 40 cm when the body was in space. The Ni59 activity indicates that the terrestrial age of Hoba is less than 80,000 years. Its Cl36-Ar36 exposure age is 263±40 million years. The Cl36 and rare-gas isotopes were also measured in the Deelfontein meteorite; its Cl36-Ar36 exposure age is 400±40 million years. The Cl36 and the Ni59 were also measured in a sample of Sikhote-Alin. In both Hoba and Sikhote-Alin the Ni59, which is a neutron-produced isotope, is higher than would be expected from the Cl36 content. This indicates that solar flares contributed to the neutron-produced isotopes in these iron meteorites.

A scintillation counter, suitable for the measurement of radioactivity in solutions irrespective of the nature of the solvent, is described. The instrument has been developed specifically for the continuous monitoring of effluents from chromatographic columns. Beads of a lithium-cerium glass, insoluble in all solvents except hydrofluoric acid, in a shallow flow-cell act as scintillator; the photons are detected with a pair of photomultipliers with coincidence circuit in conjunction with a ratemeter. The efficiency of counting 14 C and 35 S in solution is better than 20%; for 32 P the efficiency is about 90%, for 36 Cl 63%, but for 3 H it is only 0.3%, depending on photomultiplier and discriminator voltages and temperature selected.

Resume Experiments on some nuclei have been performed with the Saclay linear accelerator using the time-of-flight method. The investigated energy range is 9–113 keV for Cl, 200–31000 eV for Cu, 20–1000 eV for Ba and 3–740 eV for Nd. The spin value is assigned to most of the resonances. Strength function values against the spin value and the mass number A are discussed.

Cl36 was prepared by neutron irradiation of C.P. grade potassium chloride for 14 months in the NRX reactor. The disintegration rate of a purified sample of the irradiated material was determined by absolute beta counting with a 4π methane flow-type proportional counter. The number of Cl36 atoms in the sample was determined by gravimetric and mass spectrometric analysis. A value of (3.08 ± 0.03) × 105 years was obtained for the half-life of Cl36, assuming that the simple decay scheme is correct.

Chloride samples from the waters of Mono Lake, Pyramid Lake and the lower Truckee River have been examined by low-level counting techniques for chlorine-36 content. Chlorine-36 in the lake samples was found to be below the limit of detectability of the method, indicating a cosmic ray exposure age of less than 300,000 years for the chloride examined. No detectable chlorine-36 was found in surface chloride samples from three separate salt-flat locations in Utah and Nevada. Significantly detectable chlorine-36 was found in the lower Truckee River sample and it is suggested that this activity has its origin in recent thermonuclear tests. Hydrogen-deuterium ratios were determined for Mono Lake, Pyramid Lake, Lake Tahoe and associated streams. It is indicated that all three lakes lose water largely by evaporation, and that Lake Tahoe water has substantial residence time despite its outflow into the Truckee River. It is also indicated that the Truckee River is subject to strong dilution by fresh runoff water.

A search for the existence of K-capture in ^(36)C1 has been made using a proportional tube spectrometer with labelled methyl chloride as a gaseous source. A peak which was observed in the beta spectrum corresponded to the K-radiation of sulphur and indicated the presence of K-capture. The branching ratio K/β^- was found to be (l·7±0·1)%. A scintillation spectrometer failed to detect any gamma-ray lines above 20 kev with intensity greater than 10^(-4) of the beta intensity, so the observed K-capture transition goes to the ground state of ^(36)S.

Levels in ${\mathrm{S}}^{36}$ and ${\mathrm{S}}^{34}$ up to about 8-MeV excitation energy have been studied with the ($d,{\mathrm{He}}^{3}$) reactions on ${\mathrm{Cl}}^{37}$ and ${\mathrm{Cl}}^{35}$, respectively. Spectroscopic factors have been extracted for four states in ${\mathrm{S}}^{36}$ and ten states ${\mathrm{S}}^{34}$. The levels at 4.58 MeV in ${\mathrm{S}}^{36}$ and 4.09 MeV in ${\mathrm{S}}^{34}$ may be the ${1}^{+}$ states that shell-model calculations predict at 5.75 and 4.97 MeV, respectively. Considerable ${d}_{\frac{5}{2}}$ strength is seen to the states between 4.71 and 8.0 MeV in ${\mathrm{S}}^{34}$, but very little is observed in much the same region of excitation in ${\mathrm{S}}^{36}$.

Time-reversal invariance was studied by measuring γ-γ coincidences in 36 Cl after the capture of polarized thermal neutrons. The contribution of the time non-invariant amplitude for γ-decay to the total amplitude was determined to be (0.8±2.3) · 10 −3 , thus indicating no violation of T -invariance.

This paper presents the results obtained in measurements of the degree of circular polarization of gamma transitions to bound states of 33 S, 36 Cl, 49 Ti, 56 Mn, 57 Fe, 60 Co and 64 Cu following the capture of polarized thermal neutrons. Spin values have been determined on the basis of these results.

Cosmic rays and nuclear explosions are adding radioactivity to the atmosphere from which it is then removed by rainfall. The investigation of these activities furnishes a means of obtaining new information of significance in geological problems as well as in the understanding of the hazards of nuclear fallout. Chlorine-36 is an interesting isotope for such a study as it has a relatively long half-life, 308,000 years, and at the same time is very soluble in water. Relatively high levels of Cl36 activity have been found in rain. The levels are several orders of magnitude above the level to be expected from cosmic-ray production. The Cl36 is almost surely the result of neutron irradiation of sea water by nuclear explosions.

Iron(III) Hydroxide was absorbed on chromatography paper and separation of radioisotopes carried out by rising chromatography. In the anion experiments (P/sup 32/O/sub 4/), (S/sup 35/O/sub 4/)/su p 2-/, and (Cl/sup 36/)/sup -/ were separated from each other. In the cation experiments Sr/sup 90/, Y/sup 90/, Cs/ sup 137/, and Ce/sup 144/ were separated f rom one another. Good results were obtained. (M.C.G.)

The reactions K/sup 39/(n,p gamma )Ar/sup 39/ and K/sup 39/(n, alpha gamma )Cl/sup 36/ ha ve been investigated using a KI(TI) charged particle detector and a Na((Tl) gamma detector. Evidence for a cascade transition from the 2.10-Mev level in Ar/sup 39/ via the 1.27-Mev level was noted, and new levels at 2.36, 2.66, and 2.76 Mev were found. Spectra and level diagrams are included. (D.C.W.)

Using a Nier-type mass spectrometer, the isotopic composition of chlorine gas obtained from natural potassium chloride has been measured to be 75.529 ± 0.016 atom per cent Cl35and 24.471 ± 0.016 atom per cent Cl37, corresponding to a Cl35/Cl37atom ratio of 3.0865 ± 0.0027. By comparison of this result with that for chlorine gas from potassium chloride irradiated for 14 months in a high flux position of the NRX reactor, the neutron capture cross-section of Cl36has been determined to be 90 ± 25 barns. This value has been calculated on the assumption that only (n, γ) reactions were significant in changing the isotopic composition of the chlorine.

Four di-, tetra-, and hexachlorobiphenyls labeled with deuterium (>98%) in specific positions have been prepared by selective hydrogenolysis of iodine from chloroiodobiphenyls with lithium aluminum deuteride. 3,3’,4,4’- Tetrachlorobiphenyl (4,4’-36Cl) and 2,2’,4,4’,- 5,5’-hexachlorobiphenyl (4,4’-36Cl) were made by the decomposition of the corresponding chlorobiphenyl diazonium fluoroborates in dimethyl sulfoxide in the presence of ferric chloride-36Cl. The 2 synthetic routes described are models for the preparation of many related compounds because a variety of amino compounds, which are starting materials in the reactions described, are readily available.

With scintillation spectrometers, angular correlations have been measured of γ-radiation following thermal neutron capture in 35Cl. The following spins in 36Cl are determined: J(0.788) = 2 or 3, J(1.949) = 2, J(1.957) = 2, J(2.469) = 3. The latter three spin assignments are based on the assumption that the 2.469 → 1.949 MeV transition has El character. The capturing state is predominantly of J = 2 character.

The radioactive isotopes Be/sup 10/, Al/sup 26/, Cl/sup 36/, K/sup 4/ / sup 0/, and Mn/sup 53/ were measured in four iron meteorites: Grant, Williamstown, Odessa, and Canyon Diablo. Each sample was recycled to constant activity, using a different chemistry for each recycle wherever possible. The samples were counted with a low-level beta -counter, except for Mn/sup 53/ whose x-rays were measured. The isotope ratios were approximately constant for each meteorite, except for Mn/sup 53/ where a depth effect is visible. The cosmic-ray ages of Williamstown and Grant are about the same. (auth)

The oxidation state assumed upon solution by 36 Cl formed by thermal neutron irradiation of chlorine-containing minerals was determined. Except for about 0·2 and 0·9 per cent as ClO 3 − in carnallite and chlorapatite, respectively, all the 36 Cl radioactivity was found in the chloride state. The 36 Cl radioactivity in the chloride state in carnallite and chlorapatite was reduced by thermal annealing.

Cl gas solubility in molten lead chloride- potassium chloride mixtures, temperature and KCl concentration dependence and existence of exchange process

In order to take full advantage of liquid scintillation measurements for low level radioactivity, a large part of the solvent should be synthesized from the material of the sample to be counted. This procedure has been applied to three natural radioactivity dating a large part of the solvent should be synthesized from the material of the sample to be counted. This procedure has been applied to three natural radioactivity dating methods. For carbon-14, the most sensitive and practical of the various liquids investigated is benzene. The compound, in addition to being a good liquid scintillation solvent, contains 92% carbon. The work on the synthesis of benzene for carbon-14 dating is now complete with yields approaching 100% and less than eight hours total chemical preparation time. Furthermore, the isotope effect for carbon has been proven to be small and reproducible to better than 1/2%. A synthesis of benzene for low level tritium measurements has also been developed. Benzene contains 8 % hydrog...

The study of the isotopic abundances of the rare gases helium, neon, and argon in iron meteorites lead to the conclusion that the rare gases are produced mainly by the action of the cosmic rays with the meteorites. The high energy cosmic ray particles produce nuclear spallation reactions with the elements composing the meteorites. By comparing the cosmic-ray produced radioactive isotopes of different half lives such as H/sup 3/, Ar/sup 37/, Ar/sup 39/, Cl/sup 36/, Al/su p 26/, Be/sup 10/, and K/sup 40/ it is possible to investigate the constancy of cosmic rays in time and space. The measurements indicate that during the last 500,000 years there was no greater than a 10% change in the intensity of cosmic rays, and that cosmic rays near the earth have about the same intensity as cosmic rays in the asteroidal belt some 450 million kilometers further from the sun. In addition there is evidence that indicates that some of the meteorites have undergone collisions in space previous to being captured by the earth. (auth)

An isotope dilution method using Cl/sup 36/ is described in which the true value of the total chloride content of a sample of biological fluid or tissue can be measured with a precision of plus or minus 0.8% (relative standard deviation) for amounts of 150 to 250 mu equiv of chloride. The method involves complete isotopic exchange of stable with added radioactive chloride in a solution formed by hot alkaline digestion of the sample, and determination of the correct value of the diluted specific activity in purified solutions obtained by successive stages of alkaline dry ashing, oxidationreduction, and distillation. Radioassay was performed by infinite thickness liquid counting, and chemical assay was by automatic coulometric-amperometric titration with siiver ion. The true chloride contents of tissues of normal adult rats, dogs, and frogs were lower than most values previously reported, particularly for muscle and liver. The isotope dilution method described can serve as a standard of reference for the evaluation and validation of simpler methods of chloride measurement in biological materials. (auth)

A number of nuclide formation cross sections were measured, using the Rerkeley 184-in. cyclotron, to assist in the interpretation of the data on cosmic- ray-produced nuclides in the atmosphere and in iron meteorites. Cross sections of H/sup 3/ and Be/sup 7/ were measured in bombardments of organic targets containing nitrogen and oxygen by protons of energy 225 to 730 Mev. Semicarbazide (CH/sub 5/N/sub 3/O) targets were used to obtain cross sections in air nuclei. The tangets were prepared by mixing with a few percent of aluminum dust to permit reliable monitoring of the beam. Polyethylene, aluminum lactate, and Plexiglas targets provided elementary cross sections in carbon and oxygen. The cross sections for the production of the long lived isotopes Cl/sup 36/ (3 x 10/sup 5/ yr) and Al/sup 26/ (8 x 10/sup 5/ yr) at 730 Mev, and of a number of short lived radionuclides at 500 and 730 Mev, in iron bombardment by protons were measured. These data and those of earlier workers suggested some modifications in empirical relations used for predicting spallation cross sections in the case of nuclides close to stability. (auth)

A method of studying the exchange of chlorine between C6H5COCl and AlCl3 labelled with 36Cl has been worked out. It consists of removing rapidly C6H5COCl from the addition compound C6H5COCl, Al[36Cl]3, formed in CS2 with p-dioxane, which in its turn gives an addition compound p-dioxane,AlCl3. The latter compound described by the authors is stable enough to be easily isolated and lends itself well for the measure of the radioactivity of 36Cl.

There has been discussion in the literature as to whether the cumulative number of levels in light nuclei varies more nearly as exp(const. [Formula: see text]) or exp(const. E), where E is the excitation energy. The question is examined in this paper. It is found that if one constructs "step diagrams" by plotting the cumulative number versus the energy, both formulas represent the data almost equally well. However, additional consideration of levels counted above neutron and proton binding energies shows that exp(const. [Formula: see text]) fails badly to represent the data, whereas exp(const. E) continues to give good fits. In either case E may be measured above an arbitrary ground-state energy E0. If the satisfactory formula is written in the form exp(E–E0)/T, then it is found that the dependence of the slope on mass number may be expressed in approximately the form T−1 = 0.0165A MeV−1, but there are significant deviations from this relation apparently related to shell structure. The intercepts E0 are quite variable but are roughly clustered according to the oddness or evenness of the neutron and proton numbers of the nucleus.

A high-sensitivity mass spectrometer was used to measure the helium, argon, and neon produced in iron by 0. 16-, 0.43-, and 3.0-Bev protons. The spectrometer has a sensitivity so that 10 /sup -11/ it standard cc of helium could be detected above the contamination level. The He/sup 4/ cross sections are 120 mb, 450 mb, and 1300 mb at 0. 16, 0.43, and 3.0 Bev, respectively, while the He/sup 3/He/sup 4/ cross section ratios are, respectively, 0.09, 0.10, and 0.18. At 0.43 Bev, cross sections of 1.0 mb, 3.3 mb, 8 mb, and 4.1 mb were found for the argon isotopes 36, 37, 38, and 39, respectively. The cross section for neon-21 is 0.1 mb at 0.43 Bev. The results are discussed in relation to evaporation theory and the rare gas coatent of iron meteorites. The He/sup 3/ yields are all higher than previously measured tritium values. At 3 Bev the He/ sup 3/T ratio is 2.4. It is suggested that in the case of iron in evaporation theory the Coulomb barrier is not as important relatively as previously thought. Alternatively, a large fraction of the He/sup 3/ and tritium may be prcduced during the nuclear cascade which precedes themore » evaporation from the excited nuclei. The cross sections measured bear directly on the cosmicray-produced rare gases in meteorites. From the cross section of directly produced He/sup 3/ relative to T, previous measurements of He/sup 3/-T exposure ages of iron meteorites must be reduced by a factor of about 3. From the argon isotope cross sections it is seen that 50% of the Ar/sup 36/ in meterites is the result of BETA decay of cosmic- ray-produced Cl/sup 36/ and thus Ar/sup 36/-Cl/sup 36/ should be a reliable method for measuring exposure ages of meteorites. (auth)« less

1. The reaction of trichlorogermane with CCl4 at 75° leads mainly to the formation of HCCl3 and GeCl4. The yield of CCl3GeCl3 under these conditions is 17%, in which connection its formation, based on the radiochemical study data, proceeds by the carbenoid mechanism, i.e., via the transfer of GeCl2 from trichlorogermane to CCl4. 2. The participation of HGeCl3 as a possible intermediate compound in the reaction of the complex C4H8O2·GeCl2 with CCl4, and probably with other organic halides, should be rejected.

The spin and parity of the 398 eV resonance in the capture of neutrons by /sup 35/Cl has been determined by the method of particle-..gamma.. directional correlations. The resonance is shown to have a spin-parity of 2/sup -/ and the process proceeds predominantly with the channel spin 2.

In the last few years, progress in radioisotope dating has been made by direct counting of radioactive isotopes rather than measuring the radioactive decay. The single atom detection can be achieved by using an electrostatic accelerator as a component of an ultra-sensitive mass spectrometer (1). For such applications the existing EN-Tandem accelerator facility at the Swiss Federal Institute of Technology, Zurich (ETH) is being modified in order to measure the isotopic composition of all elements of interest with Z ⩽ 53.

Measurements have been made of the ratios of chlorine-36 to chlorine in five halite samples from Searles Lake sediments, previously dated by carbon-14, thorium-230, and magnetostratigraphic techniques. The ages calculated from the chlorine ratios are generally concordant with those from the other methods, implying the constancy of the chlorine input ratio over the last million years.

The isotope ratio in metal deposits obtained by sputtering a flat target at low ion energy (100 eV) under normal ion incidence is a function of the ejection angle. The lighter isotope (s) are enriched in the direction normal to the target surface as result of ’’reflective collisions’’ which occur when an atom collides with one of heavier mass underneath. Experimental results are presented for Cu(63‐65) and the seven Mo isotopes.