State-to-state rotational transition rates of the HCO+ ion by collisions with helium |
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| Authors: | G Buffa L Dore M Meuwly |
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| Institution: | IPCF-CNR, Largo Pontecorvo 3, 56127 Pisa, Italy;Dipartimento di Chimica 'Ciamician', Universitàdi Bologna, Via Selmi 2, 40136 Bologna, Italy;Department of Chemistry, Klingelbergstr. 80, 4056 Basel, Switzerland |
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| 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  decrease for increasing values of j and Δ 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. |
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| Keywords: | molecular data ISM: molecules |
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