The rates of rotational transitions for HCO+, the most abundant ion in interstellar space, induced by collision with helium are obtained for temperatures ranging from 10 to 80 K. The calculations are based on a new potential energy surface for the He–HCO+ interaction and on a scattering matrix whose accuracy was checked by pressure broadening and shift measurements. The rates qjj decrease for increasing values of j and j, with a temperature trend depending on the energy involved in the transitions: if it is small, the rates are almost constant, while an increase with T is found for other cases. Comparison with previous and less accurate results shows an agreement within 50 per cent. Comparison between state-to-state and pressure broadening cross-sections allows us to discuss importance and influence of elastic and inelastic collisions.
State-to-state rotational transition rates of the HCO+ ion by collisions with helium / G. Buffa; L. Dore; M. Meuwly. - In: MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY. - ISSN 0035-8711. - STAMPA. - 397:(2009), pp. 1909-1914. [10.1111/j.1365-2966.2009.14890.x]
State-to-state rotational transition rates of the HCO+ ion by collisions with helium
DORE, LUCA;
2009
Abstract
The rates of rotational transitions for HCO+, the most abundant ion in interstellar space, induced by collision with helium are obtained for temperatures ranging from 10 to 80 K. The calculations are based on a new potential energy surface for the He–HCO+ interaction and on a scattering matrix whose accuracy was checked by pressure broadening and shift measurements. The rates qjj decrease for increasing values of j and j, with a temperature trend depending on the energy involved in the transitions: if it is small, the rates are almost constant, while an increase with T is found for other cases. Comparison with previous and less accurate results shows an agreement within 50 per cent. Comparison between state-to-state and pressure broadening cross-sections allows us to discuss importance and influence of elastic and inelastic collisions.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.