PREDICTION OF THE TEMPERATURE-DEPENDENT STATIC FORM FACTOR IN HEI AND HE II.
Research communication no. 16,
DOUGLAS AIRCRAFT CO INC HUNTINGTON BEACH CALIF ADVANCED RESEARCH LAB
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A method is presented for predicting the temperature-dependent properties of the static form factor in HeI and HeII at low momenta. The prediction is based upon the observation that a single coherent, collective mode of excitation predominates for temperatures theta or 2.57K and momenta k approx 10.6A. An expression is developed for the dissipative part of the density-density response function CHIk, omega in the collisionless regime. This result exhibits a slight temperature-dependent energy shift in the position of the main resonance from its value at theta 0K. However, the sharp resonance structure is retained, reflecting the fact that the collective mode, which is the principal contributor to CHIk omega in the regime considered, exists as a nearly independent mode of excitation for all temperatures theta or 2.57K. The expressions for the dynamic and static form factors are derived. They appear to be insensitive to superfluid behavior. The temperature dependence of the static form factor Sktheta for 0 or theta or 2.57K is summarized by the inequalities delta-Skdelta-theta 0 for k 10.38A and delta-Skdelta-theta 0 for k 10.38A. Author
- Quantum Theory and Relativity