Mon. Not. R. Astron. Soc., 444, 2544-2554 (2014/November-1)
Collisional excitation of singly deuterated ammonia NH2D by H2.
DANIEL F., FAURE A., WIESENFELD L., ROUEFF E., LIS D.C. and HILY-BLANT P.
Abstract (from CDS):
The availability of collisional rate coefficients with H2 is a pre-requisite for interpretation of observations of molecules whose energy levels are populated under non-local thermodynamical equilibrium conditions. In the current study, we present collisional rate coefficients for the NH2D/para-H2(J2 = 0, 2) collisional system, for energy levels up to Jτ = 77 (Eu ∼ 735 K) and for gas temperatures in the range T = 5-300 K. The cross-sections are obtained using the essentially exact close-coupling (CC) formalism at low energy and at the highest energies, we used the coupled-states (CS) approximation. For the energy levels up to Jτ = 42 (Eu ∼ 215 K), the cross-sections obtained through the CS formalism are scaled according to a few CC reference points. These reference points are subsequently used to estimate the accuracy of the rate coefficients for higher levels, which is mainly limited by the use of the CS formalism. Considering the current potential energy surface, the rate coefficients are thus expected to be accurate to within 5 percent for the levels below Jτ = 42, while we estimate an accuracy of 30 percent for higher levels.