| Popis: |
Partial differential cross sections for the scattering of neutrons of 0.0150, 0.0252, 0.0706, 0.103, and 0.142 ev initial energy into angles of l6.3 deg , 26.0 deg , 36.4 deg , 47.6 deg , 59.5 deg , 72.1 deg and 84.7 deg from samples of room temperature methane gas are presented. These are converted to scattering law and are compared to three calculations: the ideal gas calculation gives limited agreement using a mass of 3.2. the average of the Sachs-Teller mass tensor; the Krieger-Nelkin approximation which includes effects of zero-point vibrations is a better fit, but underestimates in the region of harge momentum transfers; a calculation using exact thermal orientation averages of the matrix elements gives the best fits. None explain the results at small energy and momentum changes; this disagreement is attributed to the classical treatment of the rotational states in these calculations. (auth) |
