15min:

D. R. WILLEY, R. E. TIMLIN JR., I. SULAI, C. C. RUGGIERO, Dept. of Physics, Allegheny College, Meadville, PA 16335.

We report low temperature pressure broadening cross sections for the (J, K) = (1, 1), (2, 2) and (3, 3) inversion transitions of NH₃ broadened by molecular deuterium from 15 to 40 K. These D₂ broadening studies serve to complement our earlier work on the low temperature pressure broadening of NH₃ by He, normal-H₂ and para-H₂. While D₂ has nearly the same mass as He, its electronic structure is similar to H₂. Owing to its greater mass and consequent decreased velocity relative to H₂, the expectation is that cross sections for NH₃ collisions with D₂ will be smaller than cross sections for H₂ at a given temperature or energy. However, experimentally we find the NH₃-D₂ cross sections are larger than for broadening by normal-H₂, J=0, para-H₂ and He.