Knowledge Bank

Pressure broadening of the (J, K)=(1, 1), (2, 2) and (3, 3) inversion transitions of $NH3$ was measured using normal- $H2$ as the broadening agent at kinetic temperatures of 15 to 40 K. Measurements were taken in a quasi equilibrium cell using the collisional cooling technique. $H2$ pressure broadening cross sections were compared to low temperature He pressure broadening of the same transitions and found to be from 2.5 to 8 times larger than corresponding He cross sections. Measured normal $H2$ and He cross sections were also compared to calculated $J=0$, para-$H2$ cross sections. Preliminary experimental results for broadening by para- $H2$ will aim be presented.