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Molecular angular momentum polarization produced in molecule–surface interaction is investigated by studying the magnetic field effect on a Knudsen flow at temperatures between 78 and 695 K. The effects for H2, D2, HD, N2, and CH4 scattered from LiF (001) are found to be 2–3 orders of magnitude larger than previously observed for other surfaces. This is attributed to the large corrugation of the LiF crystal face, since the polarization type involved depends entirely on the existence of in-plane forces. The production matrix elements are found to be on the order 10−1–10−2. Both ‘‘alignment’’ and ‘‘orientation’’ type of polarization are produced. The data indicate that the production of alignment primarily stems from purely reorienting collisions (i.e., ΔmJ transitions with ΔJ=0) while orientation tends to be produced from rotationally inelastic collisions (i.e., transitions with ΔJ≠0). The off-center rotation of HD is found to play only a minor role in the nonspherical part of the interaction producing these polarizations.

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