Knowledge Bank

Collision diameters for ten Q branch transitions in the rotational spectrum of HCOOH have been determined using pressure broadening of the spectral lines. Transitions of the type $\Delta J=0,\Delta K+1=1$, with 3 $\le$ J $\le$ 32 were investigated for both self broadening and foreign-gas broadening ($H2$ and He) of the spectral lines. Pressure ranges from 1.0 mTorr to 25.0 mTorr were explored in obtaining the linewidth parameters $\Delta \nu p$ for each transition. Collision diameters calculated from these data were found to be nearly constant over the J states for HCOOH-$H2$ and HCOOH-He interactions but showed a marked dependence on J for HCOOH-HCOOH interactions.