The Disintegration of Lithium by Deuterons

Williams, John H.; Shepherd, William G.; Haxby, R. O.

doi:10.1103/physrev.52.390

Cited by 41 publications

(11 citation statements)

References 13 publications

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“…However, this state has been well established as a resonance in the n-a scattering cross section, 5 -6 and as peaks in the spectra from at least ten different reactions, the one most frequently investigated being Li 7 (d,a)He 5 . [7][8][9][10][11][12][13][14][15] Moreover, the anisotropy of the particles emitted in the decay of the ground state has been observed by several people, and supports an assignment of P3/2 to this state. (A P1/2 assignment requires an isotropic distribution of the particles resulting from the disintegration of He 5 .)…”

Section: Introductionmentioning

confidence: 89%

First Excited State ofHe5

Fessenden

Maxson

1964

Phys. Rev.

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The reaction Li 7 (d,a)He 5 was studied with the use of coincidence circuitry and solid-state chargedparticle detectors. Targets of natural and isotopic lithium were bombarded with 150-200 keV deuterons, and a particles emitted at laboratory angles of 90 and 82 deg were detected in coincidence. The (d,a) reaction proceeding to the ground state of He 5 was observed, its differential cross section at 90 deg was measured relative to that for Li 6 (d,a)ce, and a value of 2.4_i,o +1 -5 was assigned to the parameter A in the function /(0) = 1-K4 sin30 which describes the center-of-mass ce-particle distribution resulting from the disintegration of He 5 . The first excited state of He 5 was found to have an excitation energy of 2.6±0.4 MeV and a width of 4.0±1.0 MeV. The intensity of the excited state alpha group was greater than that of the ground-state group by a factor of about 1.5. There was no evidence for any other excited state up to at least 7 MeV. The ratio of the differential cross sections at 90 deg for Li 6 (d,p)Li 7 and Li 6 (d,a)a was determined for several values of Ed and found to agree with reported cross-section data. 9 F.

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Section: Introductionmentioning

confidence: 89%

First Excited State ofHe5

Fessenden

Maxson

1964

Phys. Rev.

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“…Its presence was indicated by a study by Williams et al (1937) of the alpha-particle spectrum from the reaction They found a continuous distribution with a superposed peak which they ascribed to the reaction…”

Section: )mentioning

confidence: 95%

“…Further investigations of the reactions of neutrons and protons with tritium (TaSehek et al 1949, Argo et al 1950, however, provided evidence for an excited state at 21.6 ~ev. Downloaded by [UQ Library] at 13:08 03 February 2015 I:[eydenburg* 1941Keitler* 1947Freier* 1949Bradeu 1951, 1.q53 Putnam 1952Kreger* 1952, Atkins 1952Wickersham 1954, 1957Cork* 1954Freemantle* 1954' Williams* 1955Teem* I955 Eisberg 1956Brockman 1956Putnam* 1956a,b Vanecian 1956Chamberlain* 1956Miller* I957 Brussel* 1957Tyren* 1957 S.C. This work was not confirmed by later studies of proton-helium scattering in which the scattered protons were analysed to see if any of them had less energy than would be expected from an elastic collision.…”

Section: Pcmentioning

confidence: 99%

The scattering of nucleons by alpha-particles

Hodgson

1958

Advances in Physics

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“…2 This resonance raises the ratio of the forward scattering cross sections of helium and hydrogen from 1.4 to 2.5 Mev to about 9 at 1 Mev. We have investigated the resonance scattering more closely by using a continuous neutron spectrum.…”

Section: Resonance Scattering Of Neutrons In Heliummentioning

confidence: 99%

“…2 Further experiments are indicated, such as simultaneous observations of dark current and fluorescence.…”

Section: Observations On the Dark Current Of A Willemite Crystalmentioning

confidence: 99%

Observations on the Dark Current of a Willemite Crystal

Herman

Hofstadter

1940

Phys. Rev.

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Separation of isotopes in the gas phase is possible by the method of "evaporative centrifuging" used by Beams and Skarstrom 6 and by Humphreys. 4 The Lindemann-Aston separation factor is proportional to exp [1/T]. I have therefore attempted to obtain a relatively large separation of the chlorine isotopes by using hydrogen chloride just above its melting point in a Beams centrifuge. The rotor was cooled to -98°C and the vapor from the liquid HC1 was pumped through the hollow spindle which formed the axle. (See reference 6 for details.) Although no analysis by the mass spectrograph of the fractions was made, the operation of the centrifuge at low temperature was demonstrated. The theoretical isotopic separation coefficient which is 1.11 at room temperature, becomes 1.25 just above the solidification temperature of hydrogen chloride if the rotor velocity is 5X10 4 cm/sec. at the boundary of the liquid-gas phase. This velocity is the highest practical in "evaporative centrifuging" with hollow rotors.The substitution of-hydrogen chloride for carbon tetrachloride results in a decrease in molecular mass and a three-hundred-fold increase in ratio of gas pressure at the rotor center to that at the gas-liquid boundary. Under these conditions the time for equilibrium across a radial sector of the rotor is reduced and an increased rate of removal seems practical'. If then the centrifuge is employed to separate isotopes, it would appear advantageous to use the hydrogen halides near their melting points to effect a partial separation of large amounts of chlorine and bromine isotopes.Some time ago the photoconductivity of a single crystal of willemite was investigated at low temperatures. 1 Several times during this study it was noticed that the dark current showed a sudden large increase at about -60°C while the crystal was warming up with the field on, and then fell to its very low initial value. Subsequent . studies on this crystal showed that this effect is obtained when the crystal is illuminated with ultraviolet light at low temperatures with field on (in our case 2000 volts/cm) and then allowed to warm up in the dark. However, if the crystal is depolarized and then warmed up in the dark with the field on, the effect observed was only about 1/100 of that obtained when the crystal was initially illuminated as described above. This small effect is probably due to the fact that the crystal was not completely depolarized. Since the rate of warming up could not be controlled conveniently with the present arrangement for cooling the crystal, no quantitative measurements were made concerning the dependence of dark current on temperature, time, and exposure to ultraviolet light. This phenomenon was observed for both X2537A and X3125A. It would doubtless occur for the whole range of wave lengths for which the crystal exhibits photoconductivity. Similar results were found when electrical contact was made with either gold (sputtered) or Aquadag electrodes.We feel that this dark current effect is probably connected with the emission...

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The Disintegration of Lithium by Deuterons

Cited by 41 publications

References 13 publications

First Excited State ofHe5

First Excited State ofHe5

The scattering of nucleons by alpha-particles

Observations on the Dark Current of a Willemite Crystal

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