scholarly journals The internal conversion coefficient for radium C

1932 ◽  
Vol 138 (836) ◽  
pp. 643-664 ◽  
Keyword(s):  
Internal Conversion ◽  
Conversion Coefficient ◽  
Atomic System ◽  
Relativistic Equation ◽  
High Energy ◽  
Internal Conversion Coefficient ◽  
Γ Rays ◽  
Γ Ray ◽  
Charged Nucleus ◽  
Special Case

It is well known that the γ-rays emitted from a radio­active nucleus are often partially absorbed by the atomic system, giving rise to secondary β-rays. From observations of the resultant γ-ray intensity, and that of the β-rays, it is possible to infer the proportion of γ-rays reabsorbed in the atomic system. This factor is called the “internal conversion co­efficient.” Its theoretical value has been discussed by Miss Swirles and R. H. Fowler. Miss Swirles treats the nucleus as an oscillating Hertzian doublet, radiating classically, and considers the radiation field as producing photoelectric transitions in the planetary electrons, according to the Schrodinger theory. The rate of emission of γ-rays from the nucleus is taken to be the classical rate of radiation of energy by the dipole, divided by hv . The values obtained in this way were about 10 times too small, except for the γ-ray of energy 14.26 x 10 5 e. v., which has an internal conversion coefficient several hundred times that given by the theory. This special case has been discussed by Fowler ( loc . cit .), and we shall not consider it here. An obvious defect in the theory is the use of Schrödinger’s equation, which may not be expected to hold so near the nucleus, or for electrons of such high energy. It therefore seemed possible that the more correct, relativistic equation of Dirac might give results in accordance with experiment in the majority of cases, and the calculation has been carried out by Casimir. The same model is used, and, for purposes of calculation, the interaction of the other electrons is neglected, so that we have a single electron in the field of a charged nucleus. For the β-rays emitted from the K-shell, we may take the actual nuclear charge in carrying out the calculation. In the case of extremely hard γ-rays, whose energies may be considered large compared with mc 2 , it is legitimate to use the asymptotic expansion for the wave function repre­senting the β-ray. If we apply this theory to the range covered by experiment, we obtain results (Casimir, loc. cit. ) which are still much too small, so that we were tempted to attribute the bulk of the conversion to some special type of interaction with the nucleus. It seems fairly certain that this must be the case for the γ-ray with hv = 14.26 x 10 5 e. v., which has an abnormally high internal conversion coefficient.

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.

scholarly journals On the absolute intensities of the strong (β-Ray lines of Ra (B + C), Th (B + C), and Ac (B + C)

1937 ◽  
Vol 158 (895) ◽  
pp. 571-580 ◽  
Keyword(s):  
Internal Conversion ◽  
Conversion Coefficient ◽  
Internal Conversion Coefficient ◽  
Theoretical Interest ◽  
Absolute Intensities ◽  
Accurate Knowledge ◽  
Γ Rays ◽  
Γ Ray ◽  
The Absolute

It is now well established that the homogeneous (β-ray groups emitted by radioactive bodies arise by internal conversion of the γ-rays. The ratio of the number of electrons emitted to the number of associated γ-ray quanta is called the internal conversion coefficient and is a quantity of considerable theoretical interest. An accurate knowledge of the absolute intensities of the (β-ray groups is of great importance in determining the internal conversion coefficient in cases where from other evidence the γ-ray intensity is known, or conversely for finding the intensity of the γ-rays by assuming theoretical or empirical values for the internal conversion coefficient.

scholarly journals Speculations concerning the α-, β- and γ-Rays of Ra B, C, C.- Part I. A revised theory of the interval absorption coefficient

1930 ◽  
Vol 129 (809) ◽  
pp. 1-24 ◽  
Keyword(s):  
Internal Conversion ◽  
Conversion Factor ◽  
Conversion Coefficient ◽  
Photoelectric Effect ◽  
Internal Conversion Coefficient ◽  
Original Intention ◽  
Normal Manner ◽  
Γ Rays ◽  
Γ Ray ◽  
Parent Atom

1. Introduction .- It is well known that the γ-ray emitted by radioactive nuclei are often very strongly absorbed in a species of photoelectric effect by the planetary electrons of the parent atom, thus giving rise to the sharp lines of the β-ray spectrum. The recent work of Ellis and Aston provides numerical values of this “internal conversion coefficient” of the γ-rays from Ra BC and Ra CCD-data which bring out more clearly than hitherto the curiosities of this coefficient (see Table I below). The present paper is the outcome of repeated discussions between Dr. Ellis and the author about possible explanations of the data. All the preliminary work was carried out in collaboration, and it was our original intention to publish our results jointly. This has proved impossible, so that the responsibility for the corrections of the calculations of this paper rests entirely on me. But the work could not have been attempted without Dr. Ellis’s help. Ellis and Aston find that this coefficient behaves so differently for different classes of β-ray line that one is even sometimes tempted to suspect a different mechanism of emission. The rather soft γ-rays of Ra BC are converted by the K-level electrons in fractions of the surprising size of 10 percent. To 25 percent., varying in a normal manner with the frequency. The harder γ-rays of Ra CC’D fall, however, into three groups. The main γ-rays of energy from 6·12 X 10 5 to 12·48 X 10 5 volts have a practically constant conversion fraction of about 0·006; those from 13·90 X 105 to 22·19 X 10 5 volts a similar constant fraction now about 0·006; those from 13.90 X 10 5 to 22·19 X 10 5 volts a similar constant fraction now about 0·0015. All these γ-rays, though most easily studied via their derived natural β-ray lines undoubtedly can be studied as γ-rays outside their parent atom. But there is a third group containing one outstanding γ-ray of 14·26 X 10 5 volts energy whose existence has been inferred only from certain associated β-ray lines, among the strongest in the spectrum. (if is it a γ-ray) is so strongly converted in the parent atom that it is doubtful if it has ever been observed as a γ-ray at all. It would be consistent with (though not necessitated by) the evidence, to assert that it is a γ-ray with an internal conversion factor unity.

scholarly journals A theory of the internal conversion of γ-rays

1932 ◽  
Vol 138 (836) ◽  
pp. 665-695 ◽  
Keyword(s):  
Internal Conversion ◽  
Conversion Coefficient ◽  
Internal Conversion Coefficient ◽  
Internal Conversion Coefficients ◽  
Order Of Magnitude ◽  
Conversion Coefficients ◽  
Γ Rays ◽  
Γ Ray ◽  
Experimental Values

The “internal conversion coefficient” of a given γ-ray is defined as the probability that the γ-ray will be absorbed by one of the planetary electrons of the atom. If we denote by α the internal conversion coefficient, and by A the probability per unit time of the emission of a γ-ray by the nucleus (the Einstein A coefficient), then the number of electrons ejected per unit time is Aα, and the number of quanta escaping unabsorbed is A(1 — α). The quantity actually measured is the ratio of these two, namely α/(l — α). Experimental values of α have been obtained by Ellis and Aston for eight of the γ-rays of Radium C, and three for Radium B. For Radium C the lines measured lie between 6 and 22 x 10 5 electron volts; the internal conversion coefficients lie between 0.006 and 0.001, and do not vary smoothly with the frequency. For three lines of Radium B of energy in the neighbourhood of 3 Xx10 5 electron volts, α is much bigger, of order of magnitude 0.2.

THE TOTAL INTERNAL CONVERSION COEFFICIENT OF THE 279-kev TRANSITION FOLLOWING THE DECAY OF Hg203 AS MEASURED BY A NEW COINCIDENCE METHOD

1962 ◽  
Vol 40 (4) ◽  
pp. 383-392 ◽  
Author(s):  
J. G. V. Taylor
Keyword(s):  
Standard Deviation ◽  
Internal Conversion ◽  
Conversion Coefficient ◽  
Internal Conversion Coefficient ◽  
Coincidence Method ◽  
Β Decay ◽  
A Value ◽  
Conversion Coefficients ◽  
Γ Ray ◽  
Total Conversion Coefficient

Using a new coincidence method, the total internal conversion coefficient for the 279-kev transition following the β-decay of Hg203 has been measured with a standard deviation of about 1%. The method which employs a 4πβ–γ coincidence arrangement is based on the differential absorption of β-particles and conversion electrons in 4π geometry. For determining the absolute efficiencies of γ-ray spectrometers or ion-chambers, the method has the advantage of yielding directly the number of γ-ray quanta emitted per Hg203 disintegration without requiring any knowledge of the K:L:M conversion ratios. Likely sources of systematic error have been investigated and their effect has been shown to be smaller than the quoted standard deviation. The value obtained is α = 0.2262 ±.0019 or γ/β = 0.8155 ±.0015, in excellent agreement with the recent β-ray spectrometer measurements of Nijgh et al. This is of interest because a number of widely differing values of conversion coefficients for this transition have been reported. If the K/(L+M+N) conversion ratio of 2.60 ±.06 found by Nijgh et al. is combined with our total conversion coefficient, a value αK = 0.1633 ±.0017 is obtained.

scholarly journals The internal conversion of γ-rays. ─II

1933 ◽  
Vol 142 (846) ◽  
pp. 215-236 ◽  
Keyword(s):  
Electromagnetic Field ◽  
Excited State ◽  
Internal Conversion ◽  
Conversion Coefficient ◽  
Lower State ◽  
Internal Conversion Coefficient ◽  
Vector Potentials ◽  
Γ Rays

1. Introduction .—The Internal Conversion Coefficient of γ-rays has recently been calculated by Hulme and by Taylor and Mott. The assumptions on which both of these calculations rest may be analysed as follows. I.—A nucleus, originally in an excited state of energy W n , radiates, corresponding to the transition to each lower state of energy W m , an electromagnetic field which may be either that of a dipole or that of a quadripole. For a dipole such a field has scalar and vector potentials given by

scholarly journals The calculation of internal conversion coefficients of γ-rays

1934 ◽  
Vol 143 (850) ◽  
pp. 674-678 ◽  
Keyword(s):  
Internal Conversion ◽  
Conversion Coefficient ◽  
Internal Conversion Coefficient ◽  
Charge Number ◽  
A Value ◽  
Internal Conversion Coefficients ◽  
Conversion Coefficients ◽  
Γ Rays ◽  
Limiting Values

The purpose of this paper is the calculation of theoretical values for the internal conversion coefficient I, of γ -rays converted K-and L 1 -shells. Hulme has obtained values for I in the K-shell assuming the radiating nucleus to emit the field of a dipole; while Taylor and Mott have assumed a quadripole field. The internal conversion coefficient has here been calculated for a number of values of hv for the L I -shell applying the theory developed by Taylor and Mott; the previous results for the K-shell have been extended and slight errors in the region of soft γ-rays have been corrected. Finally, the limiting values for very soft γ -rays have been obtained for both K-and L I -shells, with both quadripole and dipole fields. The calculations have been carried through using a value of the charge number Z = 84. The correction for RaB (Z = 82) would be small. Recently Taylor and Mott have extended their theory to account for the interaction between nucleus and the extranuclear electrons. They have shown that the "internal conversion coefficients" as calculated in H II and TM I are not a measure of the ratio Number of β-particles ejected in time dt /Number of γ -quanta leaving the nucleus in time dt , but, apart from a factor in general effectively unity, give I ≡ Number of β-particles ejected in time dt /Number of γ -quanta escaping from the system in time dt .

scholarly journals The internal conversion coefficient for γ-rays

1936 ◽  
Vol 155 (885) ◽  
pp. 315-330 ◽  
Keyword(s):  
Internal Conversion ◽  
Conversion Coefficient ◽  
Theoretical Interpretation ◽  
Nuclear Model ◽  
Internal Conversion Coefficient ◽  
Γ Rays

1—The theory of the internal conversion of γ-rays has recently been discussed by several authors. The purpose of the present paper is to make a summary of the results achieved, to compare them with experiment, and to attempt a new theoretical interpretation in terms of a nuclear model.

scholarly journals The nuclear β -spectra of thorium B→C and C→C', and the intensities of some β -ray lines of thorium (B+C+C")

1948 ◽  
Vol 195 (1042) ◽  
pp. 287-300 ◽  
Keyword(s):  
Internal Conversion ◽  
Conversion Coefficient ◽  
Energy Transition ◽  
Detailed Comparison ◽  
High Energy ◽  
Internal Conversion Coefficient ◽  
Dipole Radiation ◽  
Allowed Transition ◽  
Forbidden Transitions ◽  
High Energy Transition

The β -spectra of Th(C+C") and Th(B+C+C") have been measured using semicircular focusing. The sources were mounted between two thin films to prevent the escape of ThC" by α -recoil. The intensities of seven of the β -ray lines were measured and the continuous spectra of ThB. C and ThC. C' were found by subtraction using the known spectrum of ThC". D. The β -ray end-point of ThC. C' is at 2·250 MeV, and the shape of the β -ray spectrum differs but little from that of an allowed transition for energies above 0·9 MeV. A detailed comparison is made with the shape of the compound spectrum required to account for the known γ -rays of ThC', using the theory of forbidden transitions. A spin change of ∆ I = ± 2 is ruled out, but ∆ I = 0 or ± 1 is possible. The β -spectrum of Th B seems to be composite with its principal end-points at 0·331 and 0·569 MeV. The intensity of the high-energy transition between the ground states is about 0·12 ± 0·02 electrons per disintegration. The K internal conversion coefficient of the F γ -ray was found to be about Q·377, 16% higher than the theoretical value for magnetic dipole radiation.

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