Neutrons from Deuteron Bombardment of Boron

1957 ◽  
Vol 10 (2) ◽  
pp. 268 ◽  
Author(s):  
JR Bird ◽  
RH Spear
Keyword(s):  
Excited State ◽  
Compound Nucleus ◽  
Ground State ◽  
Angular Distributions ◽  
Particle Model ◽  
Upper Limit ◽  
First Excited State ◽  
Compound Nucleus Formation ◽  
Deuteron Bombardment ◽  
Peak Widths

A natural boron target has been bombarded by 920 keV deuterons, and the emitted neutrons detected using nuclear emulsions. A new procedure for analysing measurements is described ; this procedure allows approximate corrections for errors in geometry in the plane of the emulsions. The dependence of resolution on various experimental factors has been studied, and the resolution achieved is indiCated by peak widths of 245 � 25keV and 360 � 50 keV at neutron energies of 9�7 MeV and 13�9 MeV respectively. The angular distributions of the neutrons from the 10B(d,n)l1C reaction corresponding to the ground state of 11C, and the neutrons from the 11B(d,n)12C reaction corresponding to the 7�66 Me V state in 12C, have been determined; both distributions may be attributed to compound nucleus formation. A search has been made for a neutron group corresponding to an excited state at about 5�5 MeV in 12C suggested by Glassgold and Galonsky (1956) on the basis of the a-particle model. An upper limit for the intensity of any such group is set at 1 per cent. of the intensity of the group corresponding to the first excited state in 12C.

Angular distributions from ( d, p ) and ( d, n ) nuclear reactions

1951 ◽  
Vol 208 (1095) ◽  
pp. 559-579 ◽  
Keyword(s):  
Excited States ◽  
Ground State ◽  
Nuclear Reactions ◽  
Energy Levels ◽  
Angular Distributions ◽  
Angular Momenta ◽  
First Excited State ◽  
Compound Nucleus Formation ◽  
Initial Nucleus

Experimental angular distributions from (d, p) and (d, n) nuclear reactions involve con­tributions from incident angular momenta much higher than is compatible with compound nucleus formation, and indicate that these reactions must proceed to a large extent by means of a stripping process. The angular distributions to be expected from a stripping process are calculated, and these are found to be very sensitive to the angular momenta which can be accepted by the initial nucleus, i.e. to the spins and parities of the energy levels involved. In any one case there is found excellent agreement between the experimental curve and just one of the possible theoretical curves, and if the spin and parity of the ground state of the initial nucleus is known, this allows of a determination of the spin and parity of the appropriate level of the final nucleus. In this way it is found, for example, that the ground state of 17 O has spin ⅝ or ⅜ and even parity, and that the first excited state of 17 O (0.88 MeV above ground) has spin ½ and even parity. Determinations are also made of the spins and parities of the ground states and several excited states of 13 C, 15 N and 28 Al. Families of theoretical curves for a variety of incident and outgoing energies are presented in order to facilitate further spin and parity determinations from future experimental results.

THE ANGULAR DISTRIBUTION OF THE Li7(t, α)He6 REACTIONS AT 240 KEV. TRITON ENERGY

1954 ◽  
Vol 32 (10) ◽  
pp. 621-629 ◽  
Author(s):  
E. Almqvist ◽  
T. P. Pepper ◽  
P. Lorrain
Keyword(s):  
Excited State ◽  
Ground State ◽  
Center Of Mass ◽  
Angular Distributions ◽  
Laboratory System ◽  
Mass System ◽  
Compound State ◽  
First Excited State ◽  
State Spin ◽  
Α Particles

The angular distributions of the Li7(t, α)He6 reactions have been measured between 41° and 139° to the beam in the laboratory system. The distribution of the 5.95 Mev. α-particles associated with the formation of ground state He6 is of the form [Formula: see text] in the center of mass system. The 4.95 Mev. α-particles associated with the formation of the first excited state of He6 are distributed isotropically within ±8%. These results are consistent with the expectation that the ground state of He6 has spin 0 and the first excited state spin 2 and suggest that the compound state, Be10, has J = 2.

A meta-analysis and review examining a possible role for oxidative stress and singlet oxygen in diverse diseases

2017 ◽  
Vol 474 (16) ◽  
pp. 2713-2731 ◽  
Author(s):  
Athinoula L. Petrou ◽  
Athina Terzidaki
Keyword(s):  
Oxidative Stress ◽  
Excited State ◽  
Singlet Oxygen ◽  
Ground State ◽  
Meta Analysis ◽  
Common Mechanism ◽  
High Electron ◽  
A Value ◽  
First Excited State

From kinetic data (k, T) we calculated the thermodynamic parameters for various processes (nucleation, elongation, fibrillization, etc.) of proteinaceous diseases that are related to the β-amyloid protein (Alzheimer's), to tau protein (Alzheimer's, Pick's), to α-synuclein (Parkinson's), prion, amylin (type II diabetes), and to α-crystallin (cataract). Our calculations led to ΔG≠ values that vary in the range 92.8–127 kJ mol−1 at 310 K. A value of ∼10–30 kJ mol−1 is the activation energy for the diffusion of reactants, depending on the reaction and the medium. The energy needed for the excitation of O2 from the ground to the first excited state (1Δg, singlet oxygen) is equal to 92 kJ mol−1. So, the ΔG≠ is equal to the energy needed for the excitation of ground state oxygen to the singlet oxygen (1Δg first excited) state. The similarity of the ΔG≠ values is an indication that a common mechanism in the above disorders may be taking place. We attribute this common mechanism to the (same) role of the oxidative stress and specifically of singlet oxygen, (1Δg), to the above-mentioned processes: excitation of ground state oxygen to the singlet oxygen, 1Δg, state (92 kJ mol−1), and reaction of the empty π* orbital with high electron density regions of biomolecules (∼10–30 kJ mol−1 for their diffusion). The ΔG≠ for cases of heat-induced cell killing (cancer) lie also in the above range at 310 K. The present paper is a review and meta-analysis of literature data referring to neurodegenerative and other disorders.

LIFETIME MEASUREMENTS OF STATES IN O18 AND Ne22

1964 ◽  
Vol 42 (6) ◽  
pp. 1311-1323 ◽  
Author(s):  
M. A. Eswaran ◽  
C. Broude
Keyword(s):  
Excited State ◽  
Ground State ◽  
Doppler Shift ◽  
State Transition ◽  
Branching Ratios ◽  
Ground State Transition ◽  
Lifetime Measurements ◽  
Doppler Shift Attenuation ◽  
First Excited State ◽  
Doppler Shift Attenuation Method

Lifetime measurements have been made by the Doppler-shift attenuation method for the 1.98-, 3.63-, 3.92-, and 4.45-Mev states in O18 and the 1.28-, 3.34-, and 4.47-Mev states in Ne22, excited by the reactions Li7(C12, pγ)O18 and Li7(O16, pγ)Ne22. Branching ratios have also been measured. The results are tabulated.[Formula: see text]The decay of the 3.92-Mev state in O18 is 93.5% to the 1.98-Mev state and 6.5% to the ground state and of the 4.45-Mev state 74% to the 3.63-Mev state, 26% to the 1.98-Mev state, and less than 2% to the ground state. In Ne22, the ground-state transition from the 4.47-Mev state is less than 2% of the decay to the first excited state.

Sign in / Sign up

Export Citation Format

Share Document