THE γ-RAYS OF THORIUM CC′

1948 ◽  
Vol 26a (5) ◽  
pp. 313-325 ◽  
Author(s):  
S. C. Fultz ◽  
G. N. Harding
Keyword(s):  
Energy Level ◽  
Long Range ◽  
Level Scheme ◽  
Electric Quadrupole ◽  
Coincidence Rate ◽  
A Value ◽  
Γ Rays ◽  
Γ Ray ◽  
Particle Group ◽  
Α Particles

At least two energy level schemes have been proposed for the ThC′ nucleus, which is excited in the β-disintegration ThCC′. That of Ellis (1933) includes three γ-rays of energies 0.726, 1.62, and 1.80 Mev., the 1.62 Mev. ray being doubtful. The level scheme of Latyschev and Kulchitsky (1940) has eight γ-rays including one of energy 2.2 Mev., for which no corresponding long-range α-particle group has been observed. The two level schemes lead to widely differing values for the total γ-ray energy of ThCC′. In the present investigation a value for the total γ-ray energy of ThCC′ has been obtained by measuring coincidences between the γ-rays of ThCC′ and the subsequently emitted α-particles of ThC′. It is shown that this value (0.14 Mev.) favors the level scheme of Ellis, including only the γ-rays of energy 0.726 and 1.80 Mev., and taking the former as electric quadrupole. It was found that under certain conditions the external bremsstrahlung excited by the β-rays of ThCC′ in the source-holder contributed appreciably to the coincidence rate. Precautions were taken to minimize this effect.

scholarly journals The association of γ-rays with the α-particle groups of thorium C

1932 ◽  
Vol 136 (829) ◽  
pp. 396-406 ◽  
Keyword(s):  
Long Range ◽  
Direct Evidence ◽  
Transition Probabilities ◽  
Essential Difference ◽  
Γ Radiation ◽  
Γ Rays ◽  
The One ◽  
Alternative Processes ◽  
Particle Group ◽  
Α Particles

As a result of the experiments of Rutherford, Ward and Lewis, it is now generally accepted that the emission of γ-rays from radioactive bodies is associated with the transitions of α-particles between stationary states in the nucleus. Direct evidence for the existence of these excited states in the case of radium C' is obtained from the several groups of long range α-particles which have been detected. Rosenblum has found that thorium C also emits several groups of α-particles, and the existence of a corresponding number of nuclear α-particle states can be safely inferred, which should also give rise to γ-radiation. This case was first discussed by Gamow, who pointed out that there was an essential difference here from radium C' In the latter body the extra α-particle states all have energy greater than the normal, and emission of the corresponding long range α-particles is a rare phenomenon, of the order of one long range particle for a million normal α-particles. The case of radium C' appears to be accounted for satisfactorily by the assumption of two alternative processes, either internal nuclear switch or α-emission from the excited state, the relative frequencies of occurrence depending on the ratio of the transition probabilities. With thorium C, however, the most intense α-particle group is not the one of lowest energy, and the groups only vary in intensity by a factor of one hundred instead of one million as with radium C' The assumption of alternative processes of γ-and α-emission would lead to values for the ratio of the transition probabilities for the two processes which are absolutely incompatible with what is known about the orders of magnitude of the probabilities of α-particle emission and radiation switch. Gamow therefore proposed that the thorium C nucleus is initially formed with its α-particles all in the gromid state and that disintegration could sometimes occur in such a way as to leave the product nucleus excited. Rosenblum gives the following data for the velocities and relative intensities of the groups from thorium C.

The 12 C(γ, 3α) reaction energy levels of 8 Be and 12 C

1955 ◽  
Vol 228 (1174) ◽  
pp. 376-396 ◽  
Keyword(s):  
Ground State ◽  
Energy Levels ◽  
Electric Quadrupole ◽  
Angular Distributions ◽  
Reaction Energy ◽  
Reaction Proceeds ◽  
Γ Ray ◽  
Relationship Of ◽  
The Relationship ◽  
Α Particles

The mechanism of the 12 C(γ, 3α) reaction, for γ-ray energies, E γ , up to about 40 MeV, has been determined from a study of over 2500 stars in nuclear emulsions. The study includes investigation of the angular distributions and correlations of the α-particles. The reaction is initiated mainly by electric-dipole and electric-quadrupole γ-ray interaction, the former being unexpectedly strong when E γ < 20 MeV. For E γ < 25 MeV the reaction proceeds mainly by transitions to the ground-state of 8 Be (spin J = 0), and to 2⋅95 ± 0⋅10 MeV ( J = 2) and 4⋅0 ± 0⋅1 MeV ( J = 2 or 4) levels of 8 Be. Transitions to levels near 6, 10 and 15 MeV (all J = 0, 2 or 4) become predominant when 25 MeV ≤ E γ <26 MeV. For E γ ≥ 26 MeV, most transitions lead to 16⋅8 ± 0⋅2 MeV ( J = 2) and 17⋅6 ± 0⋅2 MeV ( J = 2, possibly 0) levels, and possibly to a further 16⋅4 ± 0⋅2 MeV ( J = 0 or 2) level, levels which have not been detected in other reactions. The reaction mechanism is interpreted in terms of competing modes of decay of a compound nucleus, demonstrating the strong influence of the isotopic spins ( T ) of the levels of 12 C and 8 Be involved. For example, the 2 + levels of 12 C involved when 16 MeV ≤ E γ <20 MeV are (unexpectedly) found to have T = 1, and the 16⋅8 and 17⋅6 MeV levels of 8 Be are also found to have T = 1. The relationship of the 12 C (γ, 3α) reaction to other 12 C photodisintegration reactions (including some new reactions established during the present experiments) is discussed.

The decay of 237Np

1976 ◽  
Vol 54 (13) ◽  
pp. 1409-1420 ◽  
Author(s):  
M. Skalsey ◽  
R. D. Connor
Keyword(s):  
Level Scheme ◽  
Low Energy ◽  
Coincidence Data ◽  
Γ Rays ◽  
Γ Ray

The decay of 237Np has been investigated from singles and coincidence γ-ray spectra acquired using Ge(Li) detectors. Forty-two γ rays have been observed and all but one have been placed in the level scheme of 233Pa. The presence of unobserved transitions of low energy has been confirmed by the coincidence data. Five new γ rays are reported here and a new level in 233Pa at 303.8 keV is proposed.

The interval between the departure of the disintegration particle and the emission of the gamma radiation

1932 ◽  
Vol 28 (1) ◽  
pp. 128-135 ◽  
Author(s):  
P. Wright
Keyword(s):  
Gamma Radiation ◽  
Γ Radiation ◽  
Γ Rays ◽  
Γ Ray ◽  
Recoil Atoms ◽  
Rough Calculation ◽  
Α Particles

Previous work on the existence and period of radium C′ is discussed with reference to an experiment of Jacobsen which provides evidence that a γ ray transformation of period comparable with that of radium C′ precedes the expulsion of α particles. It is shown that, from Jacobsen's results, part of the γ radiation from a source of recoil atoms should originate in the space surrounding the source.A rough calculation is made which shows that the γ rays above the source should be detectable by ordinary methods, and a description is given of an ionisation method capable of detecting the effect. The γ rays predicted by Jacobsen's experiment were tested for by using specially prepared sources of radium C. Phenomena associated with α recoil were also investigated for sources of radium (B + C) and thorium (B + C).No evidence of a γ ray emission from the space above any of the sources was obtained. The negative result indicates that the interval between the departure of the disintegration particle and the emission of the γ ray quantum is considerably less than 10−5second.

scholarly journals The γ-rays of radium (B + C) and of thorium (C + C')

1934 ◽  
Vol 143 (849) ◽  
pp. 350-357 ◽  
Keyword(s):  
Long Range ◽  
Published Data ◽  
Level System ◽  
The Past ◽  
Rigorous Test ◽  
Γ Rays ◽  
The Absolute ◽  
Relative Measurements ◽  
Α Particles

Reliable information about the γ-rays emitted by radium C' is particularly valuable since the main features of the nuclear level system are shown by the groups of long range α-particles and are hence accessible to direct investigation. These long range groups of α-particles have been measured recently by Rutherford, Lewis and Bowden by a greatly improved method which has not only brought to light several new groups, but in addition has given considerably greater accuracy in the determination of the energies of the groups than had been possible in the past. The energy of these groups in excess of that of the normal group is a measure of the excitation energy of the nucleus and the older measurements had indicated, as was to be expected, a close correspondence between these energies and the quantum energies of the γ-rays. The recent more accurate measurements of Rutherford, Lewis and Bowden provided the opportunity of a more rigorous test of this connection and showed the possibility, by the combination of the information from these two sources, of a direct experimental determination of the level system. However, the accuracy of the published data on the Ra C γ-rays deduced from the natural β-ray spectrum was subject to some doubts for the following reasons. The measurements dated from 1924 when the absolute energies of certain strong groups in the β-ray spectrum were measured and the energies of the remaining lines determined by relative measurements. The strong groups in question lay between 0.4 X 10 5 and 3.0 X 10 5 volts and the procedure of step-wise comparision up to energies of over 2 X 10 6 volts may have led to cumulative errors. More serious was that recent measurements on the Th (B + C) β-ray spectrum had thrown doubt on the correctness of the absolute values. Lastly, experiment gives values for H ρ , that is the momenta of the electrons in the groups, and the calculation of the energies involves e / m . The older data had been based on e / m = 1.769 X 10 7 , and while the change to the value 1.760 X 10 7 alters the energies proportionally far less, there was involved here an avoidable error which had to be removed.

scholarly journals The ranges of the α-particles from the radioactive emanations and “A” products and from polonium

1932 ◽  
Vol 136 (829) ◽  
pp. 349-363 ◽  
Keyword(s):  
Long Range ◽  
Point Of View ◽  
Counting Methods ◽  
Γ Rays ◽  
The Mean ◽  
High Degree ◽  
Α Particles

The analysis of groups of α-particles by new counting methods has been described in previous papers, in which details have been given of the examination of the α-particles emitted by radium-C and -C' thorium-C and -C', and actinium-C and -C', including the long range particles. The methods have the advantage that any appreciable inhomogeneity of a group of α-particles is readily detected, and moreover, the mean range of a group may be directly measured with a high degree of precision. The experiments have now been extended to an examination of the α-particles emitted by the emanations and “A” products of the three radioactive series, and by polonium. The examination of these α-ray groups is not only of great interest from the point of view of the radioactive transformations, but also for the possible connection with the emission of γ-rays.

scholarly journals The rate of emission of alpha particles from radium

1928 ◽  
Vol 121 (787) ◽  
pp. 367-380 ◽  
Keyword(s):  
Heat Evolution ◽  
Alpha Particles ◽  
The Other ◽  
Decomposition Products ◽  
A Value ◽  
Considerable Portion ◽  
Γ Ray ◽  
Recoil Atoms ◽  
Energy Relations ◽  
Α Particles

A knowledge of the number, Z, of α particles disintegrations taking place in unit mass of radium in unit time is of considerable importance in the interpretation of radioactive changes, and, in particular, of the energy relations involved. The heat evolution of radium and its short-lived decomposition products has been studied by a number of workers. Most of the heat production is accounted for by the energy of the a particles and recoil atoms, and in any particular experiment an allowance may be made for the β and γ ray energy absorbed. The experimental results are in agreement with the energy calculated from the number and energy of the a particles if a value is assumed for Z of about 3.7 . 10 10 . If, on the other hand, the value 3.57.10 10 obtained by Rutherford and Geiger, or the value 3.40.1010 recently published by Geiger and Werner, be taken, the calculation leaves a considerable portion of the heating effect unaccounted for, and this would involve an unidentified heatproducing mechanism in the disintegration.

The number of α-particles emitted by thorium C + C′

1928 ◽  
Vol 24 (1) ◽  
pp. 133-138 ◽  
Author(s):  
S. W. Watson ◽  
M. C. Henderson
Keyword(s):  
Γ Rays ◽  
Γ Ray ◽  
Α Particles

The number of α-particles emitted per second by thorium (C + C′) has been determined by an ionisation method. The number obtained is 4·26 ± ·08 × 1010 α-particles per second per curie equivalent γ-ray activity when in equilibrium with radio-thorium and when measured by the γ-rays of thorium C″ through 18 mm of lead. The result agrees within 1 per cent, with that extrapolated from Shenstone and Schlundt's values.The same apparatus was used to determine the slope of the Bragg curve over the first three centimetres of the range. The data fit the curve as given by I. Curie and Behounek within the accuracy of experiment. The curve given by G. H. Henderson falls too rapidly as it approaches the axis of ordinates.

The Intensity of the γ-Rays emitted by the Active Deposit of Thorium

1936 ◽  
Vol 32 (2) ◽  
pp. 328-335 ◽  
Author(s):  
F. Oppenheimer
Keyword(s):  
Energy Level ◽  
Total Energy ◽  
Internal Conversion ◽  
Conversion Coefficient ◽  
Internal Conversion Coefficient ◽  
Two Factors ◽  
Γ Rays ◽  
Γ Ray ◽  
Thorium Series ◽  
Made In

1. Ellis(1) has proposed energy level systems for the bodies of the Thorium series, but the values of the γ-ray intensities forming the basis of this system fail to account satisfactorily for the total energy of the γ-rays emitted by Th C and its products. This is a serious discrepancy which needs examination. Since the publication of these level systems, we have obtained new values for the intensities of the γ-rays from Th C and Th Pb. The details of these measurements are given in the second part of this paper. These γ-ray intensities are, of course, deduced from the intensities of the discrete β-groups by dividing by the appropriate internal conversion coefficient. The changes which we have made in the γ-ray intensities are due first to revised values of the β-ray intensities from Th Pb and secondly to a revised set of values of the internal conversion coefficient (2). We have not however found it necessary to make any change in Ellis and Mott's (3) allocation of lines to dipole or quadripole type. The contributions of the two factors are made clear in Table I.

THE DECAY OF Au193 AND LEVEL SCHEME OF Pt193

1957 ◽  
Vol 35 (5) ◽  
pp. 672-692 ◽  
Author(s):  
G. T. Ewan
Keyword(s):  
Excited State ◽  
Electron Capture ◽  
Level Scheme ◽  
Half Life ◽  
Internal Conversion ◽  
Upper Limit ◽  
First Excited State ◽  
Γ Rays ◽  
Γ Ray ◽  
Conversion Spectrum

Au193 has been produced as the daughter of Hg193 formed by the reaction Au197(p, 5n)Hg193 in the McGill synchrocyclotron. The internal conversion spectrum and unconverted γ-ray spectrum have been examined using β-ray spectrometers, Nal spectrometers, and coincidence techniques. Au193 decays by electron capture to Pt193 with a half-life of 17.5 ± 0.2 hr. An upper limit of 0.08% per disintegration has been placed on the probability of emission of positrons in this decay. Twenty-eight γ-rays, all below 500 kev., have been observed associated with the decay of Au193. The first excited state of Pt193 has been shown to be at 12.7 kev. and the lifetime of this state measured as (2.2 ± 0.8) × 10−9sec. A level scheme is proposed for Pt193.

Sign in / Sign up

Export Citation Format

Share Document