scholarly journals Artificial disintegration by radium C' α-particles-aluminium and magnesium

1934 ◽  
Vol 146 (857) ◽  
pp. 396-419 ◽  
Keyword(s):  
Experimental Evidence ◽  
Nuclear Energy ◽  
Absorption Curve ◽  
Discrete Groups ◽  
Light Elements ◽  
Atomic Nuclei ◽  
Scintillation Method ◽  
Electrical Methods ◽  
Α Particles

A study of the protons emitted from certain elements when bombarded by α-particles has yielded valuable information on the structure of the atomic nuclei of light elements. The development of electrical counters for α-particles and protons has provided a method by which the emitted protons can be analysed in a more detailed manner than was possible by the scintillation method. These electrical methods have been applied to the examination of the protons emitted from many elements when bombarded by α-particles. For several elements the absorption curve of these protons reveals the presence of a number of discrete groups of protons each ending at a definite range. It is a found that an α-particle of given energy may give rise to one or more groups of protons, each group corresponding to a transmutation process in which a definite amount of nuclear energy is either absorbed or released. It also appears that α-particles of all energies are not equally effective in producing protons, since the energies of the α-particles which produce protons fall into definite discrete groups. The experimental evidence so far obtained has been co-ordinated by adopting the picture of the nucleus shown in fig. 1.

Utilization of the nuclear energy of the light elements

1991 ◽  
Vol 161 (5) ◽  
pp. 171-175 ◽  
Author(s):  
Yu.B. Khariton ◽  
Ya.B. Zeldovich ◽  
I.I. Gurevich ◽  
I.Ya. Pomeranchuk
Keyword(s):  
Nuclear Energy ◽  
Light Elements

scholarly journals Some nuclear transformations of beryllium and boron and the masses of the light elements

1935 ◽  
Vol 150 (869) ◽  
pp. 241-258 ◽  
Keyword(s):  
Spontaneous Emission ◽  
Periodic Table ◽  
Small Error ◽  
The Other ◽  
Light Elements ◽  
Mass Energy ◽  
Present Communication ◽  
Mass Data ◽  
The Masses ◽  
Α Particles

In a recent paper we showed that the nuclear transformations produced in lithium by bombarding the element with protons and with ions of heavy hydrogen were in complete accord with the laws of the conservation of mass-energy and of momentum. At the same time we pointed out that there were serious discrepancies between the mass-data and the transformation-data in some other cases, and we stressed the fact that the concordance for lithium was one between mass-differences, and gave no test of the correctness or otherwise of the absolute masses in terms of O 16 = 16·000. In the present communication we present the results of experiments on the transformation of beryllium and boron by protons and by ions of heavy hydrogen. It is shown that it is not possible to interpret these results on the mass-data at present available, and we indicate how the difficulties may be overcome by the assumption of a single small error in the mass-spectrographic value for the mass of He 4 . Beryllium So far as it is known beryllium consists of a single isotope,* the mass of which according to Bainbridge is 9·0155. This mass is greater than that of two α-partieles and a neutron (8·0043 + 1·0080§ = 9·0123) by nearly three million volts, and hence great difficulties have been en­countered in nuclear theory in accounting for the observed stability. It had been found by Rayleigh|| that the mineral beryl contained an abnormal quantity of helium, while the experiments of Curie-Joliot and of Chadwick¶ had shown that beryllium gave a copious emission of neutrons when bombarded by α-particles, but the most careful search has failed to give any evidence whatever for a spontaneous emission of particles from the element. Both lithium and boron, of atomic numbers 3 and 5 respectively, are very easily transformed by bombardment wit protons and with ions of heavy hydrogen, so that it was to be expected that beryllium, which lies between them in the periodic table, would also give effects when bombarded by the same ions. Observation of the energies evolved if the reactions are known with certainty, should then lead to values for the mass of Be 9 in terms of the masses of the other products of the transformations, which can be used to check the mass found by Bainbridge.

scholarly journals The anomalous scattering of protons in light elements

1936 ◽  
Vol 157 (891) ◽  
pp. 302-310 ◽  
Keyword(s):  
Single Scattering ◽  
Anomalous Scattering ◽  
Light Elements ◽  
Inverse Square Law ◽  
Atomic Nuclei ◽  
Coulomb Law ◽  
Scattering Material ◽  
Thick Layers

By a study of the scattering of protons by atomic nuclei we can gain information about the interactions of these particles. For sufficiently low velocities of the impinging protons, corresponding to 30 electron kilovolts, it has been shown by Gerthsen that they are scattered by celluloid according to the Rutherford law, and by hydrogen according to the Mott law of scattering of similar particles. At a distance of approach represented by this energy, the inverse square law of force still holds between the particles. Schneider has investigated the scattering of protons of energies up to 300 e.-kv. in aluminium, carbon, and boron. He found a pronounced maximum in the scattering by boron, compared with that by aluminium, at 200 e.-kv. It is not possible to say whether this anomaly is due to a breakdown in the Coulomb law of force between the boron nucleus and a proton, as he used thick layers of scattering material, a fact which renders the interpretation of his results difficult. The present work was undertaken with a view to checking these results, using sufficiently thin targets to ensure single scattering. Schneider’s observations have not been confirmed, although other anomalies have presented themselves.

scholarly journals Transmutation of the lithium isotope of mass seven by deuterons

1936 ◽  
Vol 157 (891) ◽  
pp. 372-385 ◽  
Keyword(s):  
Relative Frequency ◽  
Mass Number ◽  
Continuous Distribution ◽  
Periodic Variation ◽  
Lithium Isotope ◽  
Light Elements ◽  
Homogeneous Groups ◽  
Stable Element ◽  
Missing Element ◽  
Α Particles

Recent investigations on the transmutations of the light elements have shown that the mass number 5 is the only one not occupied by a stable element. In a letter to ‘Nature,’ Dr. Oliphant has pointed out that the mass defects of the light elements show a periodic variation, and has deduced from this that the missing element should have a mass of about 5·0125. It is to be expected that the place should be occupied either by an isotope of helium or of lithium of mass five, but more probably by the former. These investigations were initially undertaken to test whether the isotope of helium of mass five arose in certain transmutations. In considering the whole field of artificial transmutations, experience has shown that practically every type of reaction which is energetically possible does take place, but the relative frequency of each reaction is governed by factors which are not yet understood. Among the light elements the nuclei 1 H, 2 D, 3 T, 3 He, 4 He, and 6 Li, 7 Li, 8 Be, etc., all appear as products of nuclear transmutations, and it is reasonable to expect that the nucleus of mass five, if it exists, should also make itself evident. For example, we might expect that the transmutation of 7 Li when bombarded by deuterons should proceed in the alternative ways: 7 Li + 2 D → 4 He + 4 He + 1 n + W 1 (1) → 4 He + 5 He + W 2 (2) → 8 Be + 1 n + W 3 . (3) The bombardment of 7 Li with deuterons is therefore a likely experiment in which to search for a 5 He nucleus. It has been shown that (1) results in a continuous distribution of α- particles with energies ranging from the lowest observable (0·6 m. e-volts) to a maximum of 8·1 m. e-volts. The reality of (2) would be revealed by the presence of two homogeneous groups of particles superimposed on this continuous distribution. The work described in this paper has been done in order to ascertain whether or not the second of the above trans­mutations does occur.

scholarly journals The structure of atomic nuclei

1936 ◽  
Vol 153 (880) ◽  
pp. 493-504
Keyword(s):  
Nuclear Reactions ◽  
Atomic Weight ◽  
The Other ◽  
Light Elements ◽  
Atomic Nuclei ◽  
Reaction Energies ◽  
Reaction Equations ◽  
Independent Reaction

In a previous paper it was shown that the energies of nuclear reactions are multiples of q = 0·000415 in atomic weight units and that the atomic weights of the light elements may be supposed equal to N (1 + b ) sq , where N and s are integer and b is a small quantity the same for all elements. In the reaction equations the terms N (1 + b ) cancel out so that the reaction energies are given by nq = Σ sq . Thus the equation 4 Be 9 + 1 H 1 = 4 Be 8 + 1 H 2 + nq gives 9 (1 + b ) + 33 q + 1 + b + 19 q = 8 (1 + b ) + 17 q + 2 (1 + b ) + 34 q + nq , so that 33 q + 19 q = 17 q + 34 q + nq which gives 52 = 51 + n , or n = 1. The number of independent reaction equations is two less than the number of elements involved so that two of the values of the energy integer s can be elected. In the previous paper the values of s for 2 He 4 1 H 1 were taken to be 8 and 19 respectively and the values of s for the other elements were calculated by means of the reaction equations.

THE RANGE OF THE ALPHA-PARTICLES FROM URANIUM II

1931 ◽  
Vol 5 (5) ◽  
pp. 567-571 ◽  
Author(s):  
S. Bateson
Keyword(s):  
Direct Measurement ◽  
Alpha Particles ◽  
A Value ◽  
Scintillation Method ◽  
Good Agreement ◽  
Α Particles

The range of the α-particles from uranium II has been determined by a scintillation method to be 3.29 ± 0.08 cm. at 15 °C. and 760 mm. This is in good agreement with Laurence's value found with a Wilson chamber. From the Geiger-Nuttall relationship the period is calculated to be 28,000 years, a value considerably less than that found recently by direct measurement.

scholarly journals On the range of α-particles in rare gases

1924 ◽  
Vol 106 (739) ◽  
pp. 622-632 ◽  
Keyword(s):  
Molecular Structure ◽  
Systematic Investigation ◽  
Stopping Power ◽  
Rare Gases ◽  
Scintillation Method ◽  
Α Particles

In a recent paper R. H. Fowler (1) has calculated the atomic stopping powers of various substances for α-rays on the basis of Henderson’s (2) theory of the loss of energy of an α-ray in passing through matter, and has drawn attention to the desirability of a systematic investigation of the range of α-rays in different media. In particular, the considerable discrepancy between experiment and theory in the case of helium made it desirable to carry out further measurements with this gas for the purpose of confirmation. Also, it was considered that experiments on the range of α-rays in such comparatively simple substances as the rare gases would yield valuable information concerning the relation between the observed values of the stopping power and those calculated by Fowler. The simple monatomic gases have the great advantage, that we are free from the complications of molecular structure and dissociations. The range of the α-particles from polonium was investigated by E. P. Adams (3) for a number of gases by a scintillation method. For convenience, taking the value of the range in air at 15°C. and 760 mm. of mercury to be 3·93 cm., the corresponding values for argon and helium were 4·18 cm. and 13·58 cm. respectively. The ranges of the α-rays from polonium and radium C in helium were found by Taylor (4) to be 17·62 cm. and 32·54 cm. respectively. It will be seen that the results of Adams and Taylor for helium are very different. The preceding values for helium and argon seem to be the only data available in the case of the rare gases.

scholarly journals Some experiments concerning the counting of scintillations produced by alpha particles.— Part I

1929 ◽  
Vol 122 (789) ◽  
pp. 304-319 ◽  
Keyword(s):  
Experimental Method ◽  
Atomic Structure ◽  
Alpha Particles ◽  
Γ Radiation ◽  
Modern Conception ◽  
Scintillation Method ◽  
Γ Rays ◽  
Α Particles

Among the various methods of detecting single a-particles, the scintillation method, because of its simplicity, is often the only one applicable. When the particles are to be counted in the presence of a strong β and γ radiation, the scintillation method is indispensable, for the scintillations produced by α-particles are easily detectable on the luminous background produced by the β and γ rays, while the electrical counter is seriously disturbed by these types of radiation. Though the counting of scintillations has been constantly used as an experimental method since 1908, and practically all the fundamental data on which the modern conception of atomic structure is based, were obtained by this method, very little systematic work has been done concerning the method itself and its limitations.

scholarly journals An investigation of the ranges of the long range α-particles from thorium C and radium C, using an expansion chamber

1929 ◽  
Vol 122 (790) ◽  
pp. 668-687 ◽  
Keyword(s):  
Long Range ◽  
Expansion Chamber ◽  
Scintillation Method ◽  
Intensive Search ◽  
Many Particles ◽  
Α Particles

The existence of the so-called long range α-particles was first pointed out by Rutherford and Wood, who found, when observing scintillations caused by α-particles from thorium active deposit, that particles were present of ranges estimated as 10·2 and 11·3 cm. in air at 760 mm. and 15° C. Later work, both by Rutherford and by Wood in 1921, showed that these long range particles were α-particles coming from the source, and in view of the possible theoretical importance of these results, Bates and Rogers in 1923-24 made an intensive search for long range particles of all ranges. From thorium C they found in all three groups, one at 11·5 cm. and two of greater range at 15·0 and 18·4 cm. respectively, but their methods were open to serious objection, and later experiments by Yamada yielded certain evidence of one group only, that at 11·5 cm. Up to this point only scintillation methods had been employed, but in 1926 Meitner and Freitag published an account of some experiments on these long range particles in which an expansion chamber was used. They detected a group of particles at 11·5 cm. in standard air and also another group at 9·5 cm. Philipp, using the scintillation method, was also able to detect the 9·5 cm. particles and obtained results agreeing closely in all respects with those of Meitner and Freitag. The long range particles from radium active deposit were first observed by Rutherford in 1919 and were subsequently studied by Bates and Rogers ( loc. cit .),who in this case also found three groups of long range particles, with ranges 9·3, 11·2 and 13·3 cm. in air. In 1924, also, Rutherford and Chadwick gave an account of a very thorough investigation of the long range particles from radium active deposit. They showed that the particles arose from radium C or its products and that those of range 9·3 cm. were certainly α-particles. They also found a group of range 11·2 cm. containing approximately one-sixth as many particles as were contained in the 9·3 cm. group.

Energy Relations in Artificial Disintegration

1929 ◽  
Vol 25 (2) ◽  
pp. 186-192 ◽  
Author(s):  
E. Rutherford ◽  
J. Chadwick
Keyword(s):  
Atomic Nucleus ◽  
Experimental Evidence ◽  
Residual Nucleus ◽  
The Other ◽  
Nitrogen Nucleus ◽  
Energy Relations ◽  
Α Particles

When certain elements are bombarded by swift α particles, protons or hydrogen nuclei are liberated which are attributed to the disintegration of the nuclei of these elements. It is now generally assumed that in such an artificial disintegration of an atomic nucleus an α particle is captured by the nucleus. Experimental evidence for this capture of an α particle has been obtained by Blackett in the case of the disintegration of the nitrogen nucleus. Blackett photographed eight disintegration collisions of an α particle with a nitrogen nucleus; in each of these the track of the α particle divided into two branches, one of which was due to the residual nucleus set in motion in the collision, and the other was due to the ejected proton. No trace of a third track to correspond to the track of the α particle after the collision was observed. Blackett therefore concluded that the α particle was captured by the nitrogen nucleus.

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