Impulse approximation in solid helium
The incoherent dynamic form factor S/sub i/(Q, ..omega..) is evaluated in solid helium for comparison with the impulse approximation (IA). The purpose is to determine the Q values for which the IA is valid for systems such a helium where the atoms interact via a potential having a steeply repulsive but not infinite hard core. For /sup 3/He, S/sub i/(Q, ..omega..) is evaluated from first principles, beginning with the pair potential. The density of states g(..omega..) is evaluated using the self-consistent phonon theory and S/sub i/(Q,..omega..) is expressed in terms of g(..omega..). For solid /sup 4/He resonable models of g(..omega..) using observed input parameters are used to evaluate S/sub i/(Q,..omega..). In both cases S/sub i/(Q, ..omega..) is found to approach the impulse approximation S/sub IA/(Q, ..omega..) closely for wave vector transfers Q> or approx. =20 A/sup -1/. The difference between S/sub i/ and S/sub IA/, which is due to final state interactions of the scattering atom with the remainder of the atoms in the solid, is also predominantly antisymmetric in (..omega..-..omega../sub R/), where ..omega../sub R/ is the recoil frequency. This suggests that the symmetrization procedure proposed by Sears to eliminate final state contributions should work well in solid helium.
- Research Organization:
- Department of Physics, University of Delaware, Newark, Delaware 19715
- DOE Contract Number:
- FG02-84ER45082
- OSTI ID:
- 5651686
- Journal Information:
- J. Low Temp. Phys.; (United States), Vol. 59:5
- Country of Publication:
- United States
- Language:
- English
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HELIUM 3
FORM FACTORS
HELIUM 4
BCC LATTICES
ENERGY-LEVEL DENSITY
HARD-CORE POTENTIAL
IMPULSE APPROXIMATION
INELASTIC SCATTERING
PHONONS
SELF-CONSISTENT FIELD
SOLIDS
CRYSTAL LATTICES
CRYSTAL STRUCTURE
CUBIC LATTICES
EVEN-EVEN NUCLEI
EVEN-ODD NUCLEI
HELIUM ISOTOPES
ISOTOPES
LIGHT NUCLEI
NUCLEAR POTENTIAL
NUCLEI
PARTICLE PROPERTIES
POTENTIALS
QUASI PARTICLES
SCATTERING
STABLE ISOTOPES
360603* - Materials- Properties