Hyperfine-resolved transition rates of the DCO+ ion by collisions with helium
Authors: Buffa G.
Autors Affiliation: CNR – Istituto Nazionale di Ottica and Dipartimento di Fisica dell’Università di Pisa, Largo Pontecorvo 3, 56127 Pisa, Italy
Abstract: The importance of rotational transition rates in the analysis of cold interstellar clouds is well known. We present results, for temperatures ranging from 5 to 80 K, for the hyperfine- resolved rotational transitions of DCO+ induced by collision with helium. Since the isotopic substitution is not expected to introduce significant changes, close-coupling calculations are based on a potential energy surface obtained for He-HCO+ and checked by accurate pressure broadening and shift measurements. The well-grounded assumption that deuterium nuclear spin is not affected by the collisions allowed us to obtain the hyperfine- resolved transition matrix elements as a sum of spin-free transition matrix elements, which account for collision dynamics, multiplied by purely geometrical factors, which account for the hyperfine dependence. The temperature dependence of the rates is weak for downward transitions j -> j\’< j, while for upward transitions (j \' > j) it can be large due to the need of energy to be transferred from translation to rotation. The dependence of the rates on j and j \’ and hyperfine propensities is discussed. The rates for quasi-elastic purely hyperfine transitions j, F -> jF \’ are also obtained.
Journal/Review: MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
Volume: 421 (1) Pages from: 719 to: 725
KeyWords: scattering; molecular data; ionsDOI: 10.1111/j.1365-2966.2012.20347.xCitations: 10data from “WEB OF SCIENCE” (of Thomson Reuters) are update at: 2019-09-15References taken from IsiWeb of Knowledge: (subscribers only)Connecting to view paper tab on IsiWeb: Click hereConnecting to view citations from IsiWeb: Click here