Rotational quenching of H2CO by molecular hydrogen: Cross-sections, rates and pressure broadening

Abstract

We compute the rotational quenching rates of the first 81 rotational levels of ortho- and para- H2CO in collision with ortho- and para-H2, for a temperature range of 10-300 K. We make use of the quantum close-coupling and coupled-state scattering methods combined with the high accuracy potential energy surface of Troscompt et al. Rates are significantly different from the scaled rates of H2CO in collision with He; consequently, critical densities are notably lower. We compare a full close-coupling computation of pressure broadening cross-sections with experimental data and show that our results are compatible with the low-temperature measurements of Mengel & De Lucia, for a spin temperature of H2 around 50 K. © 2013 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.