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 Analysis of α-rays by an annular magnetic field

1933 ◽  
Vol 139 (839) ◽  
pp. 617-637 ◽  
Keyword(s):  
Magnetic Field ◽  
Long Range ◽  
Resolving Power ◽  
Counting Method ◽  
Range Measurements ◽  
Considerable Uncertainty ◽  
Radioactive Substances ◽  
Γ Rays ◽  
The Mean ◽  
Α Particles

In previous papers an account has been given of a new counting method for analysing the groups of α-rays emitted by radioactive substances, and for measuring directly their mean range in air. In the course of these experiments, we showed that the long range groups of α-particles from radium C' are very complex, consisting of at least nine groups, with mean ranges lying between 7·7 and 11·6 cm. of air. As it is believed that the energies of these long range groups are intimately connected with those of the γ-rays from radium C', it has become of great importance to determine the energies of these groups of particles with precision. As, however, the seven groups with ranges between 9·5 and 11·6 cm. differ so little in velocity that they can only be partially resolved in range measurements, it was very difficult in our experiments to determine the mean ranges with accuracy. Moreover, there has been considerable uncertainty as to the precise relation between the range and velocity of such long range particles. A much greater resolving power can be obtained by a direct velocity determination, using a magnet to bend the α-rays into a circle. The great Paris electromagnet has been used in this way by Rosenblum, who photographed the α-ray spectra produced by the well-known focussing method. He has demonstrated the complexity of a number of α-ray groups, and has measured their velocities with an accuracy of at least 1 in 1000.

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 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 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 Analysis of the long range α-particles from radium C' by the magnetic focussing method

1933 ◽  
Vol 142 (846) ◽  
pp. 347-361 ◽  
Keyword(s):  
Long Range ◽  
Energy Levels ◽  
Resolving Power ◽  
Complete Analysis ◽  
Direct Information ◽  
Annular Ring ◽  
Excited Nucleus ◽  
Counting Methods ◽  
Ring Magnet ◽  
Α Particles

In our last paper we gave an account of an annular ring magnet capable of focussing groups of α -particles after they have traversed a semicircle of 40 cm. radius. By this method the velocities of a number of important groups of α -particles were measured with a relative accuracy, it is believed, of 1 in 5000. Preliminary measurements were described of the two long range groups from thorium C´ and of two from radium C´. In a previous paper we had shown by means of counting methods that the long range groups of α -particles from radium C´ were much more complicated than those from thorium C´, and consisted of at least nine distinct groups. This older method, however, had not sufficient resolving power to separate completely a number of these groups, and the annular ring magnet was constructed primarily to make a more complete analysis of this α -ray spectrum. It is hardly necessary at this stage to emphasize the importance of accurate measurements of the energies of these groups, for they give us direct information of the energy levels of the α -particle in an excited nucleus, which is of fundamental importance in considering the question of the origin of the γ -rays from radium C´.

scholarly journals The origin of the γ -rays

1931 ◽  
Vol 132 (820) ◽  
pp. 667-688 ◽  
Keyword(s):  
Excited States ◽  
Long Range ◽  
Normal Mode ◽  
Ground State ◽  
Point Of View ◽  
Stationary States ◽  
Great Weight ◽  
Wave Mechanics ◽  
Order Of Magnitude ◽  
Γ Rays

In a recent paper, Rutherford, Ward and Lewis have described the results of their measurements on the long-range α -particles emitted by radium C. They were able to identify nine groups of α -particles of different energies in addition to the group characterising the normal mode of disintegration. It was pointed out how the modern theories of α -particle disintegration based on the wave mechanics make it possible to infer from these results the existence of a corresponding number of excited states of the radium C' nucleus. The excess of the energies of these stationary states over that of the ground state responsible for the normal α -particle are shown in Table I. It was shown that not only were these energy differences of the order of magnitude of the energies of the γ -rays emitted by radium C' immediately after the expulsion of the β -particle from radium C, but that there were several instances of numerical agreement, which lent great weight to the suggestion that the γ -rays were due to transitions of α -particles. We propose in this paper to consider this point of view in more detail and to examine some consequences that emerge.

scholarly journals The average energy of disintegration of radium E

1927 ◽  
Vol 117 (776) ◽  
pp. 109-123 ◽  
Keyword(s):  
Average Energy ◽  
The Body ◽  
Secondary Process ◽  
Characteristic Energy ◽  
Γ Radiation ◽  
Wide Range ◽  
Continuous Energy Spectrum ◽  
The Mean ◽  
High Degree ◽  
Α Particles

The problem of the velocity of the particles emitted from the nuclei of dis integrating radioactive atoms has always attracted considerable attention. It was early established that in the case of the α-rays all the particles from one substance were emitted with the same velocity, and the latest experiments of Briggs have emphasised the high degree of homogeneity attained. This result, showing that each disintegration involves exactly the same emission of energy, is easily reconcilable with our general ideas of the radioactive processes, and, as is well known, there is undoubtedly some connection between this characteristic energy and the mean life of the body. The behaviour of the β-ray bodies is in sharp contrast to this. In place of the α-particles all emitted with the same energy, we find that the disintegration electrons coming from the nucleus have energies distributed over a wide range. For example, in the case of radium E this continuous energy spectrum formed by the disintegration electrons has an upper limit at 1,050,000 volts, rises to a maximum at 300,000 volts, and continues certainly as low as 40,000 volts, and similar results have been obtained for other β-ray bodies. If this result is interpreted as showing that different disintegrating nuclei of the same substance emit their disintegration electron with different energies, we must deduce that in this case the energy of disintegration is not a characteristic constant of the body, but can vary between wide limits. Many workers have considered this to be so contrary both to the ideas of the quantum theory and the definiteness shown by radioactive disintegration that they have asserted the inhomogeneity must be a result of some secondary process, such as collision with the extranuclear electrons or emission of general γ-radiation, and that although we cannot observe them before they become inhomogeneous, the disintegration electrons are actually emitted from the nucleus with a definite characteristic energy as in the case of the α-particles.

scholarly journals A redetermination of the velocities of α particles from radium C, thorium C and C'

1928 ◽  
Vol 118 (780) ◽  
pp. 549-557 ◽  
Keyword(s):  
Electric Fields ◽  
Experimental Error ◽  
Atomic Weight ◽  
Mean Value ◽  
Experimental Result ◽  
Slow Moving ◽  
The Mean ◽  
High Degree ◽  
Active Substances ◽  
Α Particles

1. The first accurate determinations of the velocity with which an α particle is expelled from a radio-active substance and of the value of E/M, the ratio of the charge to the mass, were made by Rutherford and Robinson by measuring the deflections in magnetic and electric fields. An α particle moving with velocity V perpendicular to the direction of a magnetic field H describes a circle of radius ρ where H ρ = MV/E. Rutherford and Robinson found for α particles expelled from radium C Hρ = 3·983 X 10 5 E. M. U. and V = 1·922 X 10 9 cm. per second. The mean value of E/M for α particles from radium emanation, radium A and radium C was 4820 E. M. U., which agreed to within the limits of experimental error with the value 4826 deduced from electrochemical data taking the atomic weight of helium as 3·998 and the value of the faraday as 9647. This value of the velocity of α particles from radium C has served as a standard from which the velocities of α particles from other radio-active substances have been calculated from the Geiger relation V 3 = k R. The present paper gives an account of a redetermination of the quantity Hρ for α particles from radium C by a method which is essentially similar to those used in previous determinations of this kind. From the value of Hρ the velocity has been calculated using the theoretical value of E/M which can be found to a high degree of accuracy from more recent determinations of the atomic weight of helium and the value of the faraday, taking into account the relativity correction for the increase in mass of the α particle. For the atomic weight of helium we may take 4·000, the value deduced by Van Laar from a consideration of the density determinations of Watson, Heuse, Taylor, and in particular of Guye’s discussion of Taylor’s results. Taking the value of the faraday given by recent determinations 9649·4 E. M. U. the value of E/M for a slow moving α particle is 4824·7 and on applying the correction for the relativity change of mass this becomes 4814·8 for the α particle from radium C, neglecting the mass of the lost electrons. It may be noted that Rutherford and Robinson’s experimental result, 4820 agrees as well with this latter value as with the value 4826 which they calculated.

scholarly journals Analysis of the α-particles emitted from thorium C and actinium C

1931 ◽  
Vol 133 (822) ◽  
pp. 351-366 ◽  
Keyword(s):  
Long Range ◽  
Special Interest ◽  
Differential Method ◽  
Automatic Method ◽  
Excited Nucleus ◽  
Γ Rays ◽  
Α Particles ◽  
Corresponding Analysis

In a recent paper, an account has been given of the analysis of the long range α-particles emitted by radium C. Nine distinct groups of α-particles were detected varying in range between 7·8 and 11·6 cm. in air. Evidence was given that the emission of γ-rays from radium C is intimately connected with the occurrence of these groups of long range α-particles, and it was concluded that the γ-rays arise from the transition of an α-particle in an excited nucleus between two levels of different energies. This question has been discussed in more detail by Rutherford and Ellis, who have advanced a tentative theory to account for the relation between the energies of the γ-rays emitted from radium C. In the present paper we give the results of a corresponding analysis of the long range α-particles from thorium C and an analysis of the groups of α-particles emitted from actinium C. In these experiments the differential method of analysis was used, as in the experiments with radium C. In the present experiments, however, instead of recording the α-particles photographically on a moving film, we have mainly employed the automatic method of counting, using thyratrons in place of the oscillograph. This method, which has been developed by one of us (C. E. Wynn-Williams), has been fully discussed in a recent paper. Here it suffices merely to refer to one or two points of special interest in connection with the present research.

Der Sommer und Herbst 2003 aus phänologischer Sicht | Summer and autumn 2003 from a phenological point of view

2004 ◽  
Vol 155 (5) ◽  
pp. 142-145 ◽  
Author(s):  
Claudio Defila
Keyword(s):  
Time Series ◽  
New Record ◽  
Point Of View ◽  
Late Spring ◽  
Mean Deviation ◽  
Leaf Shedding ◽  
The Mean ◽  
Very High ◽  
Selection Of

The record-breaking heatwave of 2003 also had an impact on the vegetation in Switzerland. To examine its influences seven phenological late spring and summer phases were evaluated together with six phases in the autumn from a selection of stations. 30% of the 122 chosen phenological time series in late spring and summer phases set a new record (earliest arrival). The proportion of very early arrivals is very high and the mean deviation from the norm is between 10 and 20 days. The situation was less extreme in autumn, where 20% of the 103 time series chosen set a new record. The majority of the phenological arrivals were found in the class «normal» but the class«very early» is still well represented. The mean precocity lies between five and twenty days. As far as the leaf shedding of the beech is concerned, there was even a slight delay of around six days. The evaluation serves to show that the heatwave of 2003 strongly influenced the phenological events of summer and spring.

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