Calculations of the low temperature pressure broadening of HCO+ rotational spectral lines by H-2

Calculations on the pressure broadening by H-2 of HCO+ rotational spectral lines have been performed in the temperature range 11-300 K. Recent low temperature measurements of the pressure broadening of the J=3-2 line at 11-30 K are reproduced to within 10-20% by the results of a capture theory. The results of Anderson theory in this temperature range, on the other hand, are low by a factor of up to approximate to 3 compared with experiment. A hybrid method is proposed, which converges to the capture theory at low temperatures and the Anderson theory at high temperatures. (C) 1996 American Institute of Physics.