Collisional excitation rate coefficients of N2H+ by He

Daniel, F. ; Dubernet, M.-L ; Meuwly, M. ; Cernicharo, J. ; Pagani, L.

In: Monthly Notices of the Royal Astronomical Society, 2005, vol. 363, no. 4, p. 1083-1091

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    Summary
    Using a recoupling technique with close-coupling spin-free calculations de-excitation rate coefficients are obtained among hyperfine transitions for He colliding with N2H+. A recently determined potential energy surface suitable for scattering calculations is used to investigate rate coefficients for temperatures between 5 and 50 K, and for the seven lowest rotational levels of N2H+. Fitting functions are provided for the Maxwellian averaged opacity tensors and for the rotational de-excitation collisional rate coefficients. The fitting functions for the opacity tensors can be used to calculate hyperfine (de)-excitation rate coefficients among elastic and inelastic rotational levels, and among the corresponding magnetic sublevels of the hyperfine structure. Certain dynamical approximations are investigated and found to be invalid