ABSTRACT
We report experimentally measured cross sections for pressure broadening of OCS by He from 4.2 to 23 K. These measurements were made in a quasiequilibrium cell using the collisional cooling technique. Cross sections were obtained for the broadening of the J=2<--1, J=3<--2, and J=4<--3 rotational transitions of OCS. Theoretical cross sections were also calculated using a recent He-OCS potential surface. While at the higher temperatures, approximately 20 K, there is only modest disagreement between experiment and theory, this disagreement increases steadily with decreasing temperature, with predicted cross sections rising steeply while the experimental data remains constant or decreases slightly. Comparisons to similar recent experimental studies are made and reasons for the observed discrepancy between experiment and theory are considered.
ABSTRACT
We report experimentally measured cross sections for pressure broadening of ammonia inversion transitions by J=0, ortho-D2 at temperatures of 18-40 K. These measurements were made in a quasiequilibrium cell using the collisional cooling technique. Cross sections for broadening of the metastable (J,K)=(1, 1), (2, 2) and (3, 3) inversion transitions ranged from 67.5 A2 for (1, 1) at 20.0 K to 100.1 A2 for (3, 3) at 25.0 K. The J=0, ortho-D2 cross sections were found to be consistently larger than previously measured cross sections for low temperature broadening of NH3 by both He and H2.
