Rotational transitions of C3N− induced by collision with H2

Abstract : Rate coefficients for state-to-state rotational transitions of C 3 N − induced by collision with both ortho-and para-H 2 are presented. Quantum calculations are performed at the closecoupling level using the uniform J-shifting method and a new potential energy surface specially developed for this purpose. Rate coefficients are obtained for state-to-state transitions among the first 28 rotational levels of C 3 N − and for temperatures ranging from 10 to 300 K. The para-H 2 rate coefficients are shown to differ strongly from the mass-scaled He rate coefficients previously computed. The ortho-and para-H 2 rate coefficients are very similar, as it was already observed for the rotational transitions of CN − and C 6 H −. There is also an unexpected similarity between the rate coefficients of the rotational de-excitations of CN − , C 3 N − , and C 6 H −. This may open door to quantitative extrapolations of the rate coefficients for larger anions.