Collisional excitation of HC3N by para- and ortho-H2

TL;DR

This paper presents new quantum and classical calculations of collisional excitation rates for HC3N by para- and ortho-H2, covering 38 rotational levels up to 300 K, aiding astrophysical observations.

Contribution

It provides the first rate coefficients for HC3N with ortho-H2 and includes hyperfine resolution, enhancing modeling of interstellar medium conditions.

Findings

Rate coefficients for HC3N-H2 collisions are calculated up to 300 K.

First collisional data for HC3N with ortho-H2 are provided.

Quantum and classical methods show good agreement in rate calculations.

Abstract

New calculations for rotational excitation of cyanoacetylene by collisions with hydrogen molecules are performed to include the lowest 38 rotational levels of HC3N and kinetic temperatures to 300 K. Calculations are based on the interaction potential of Wernli et al. A&A, 464, 1147 (2007) whose accuracy is checked against spectroscopic measurements of the HC3N-H2 complex. The quantum coupled-channel approach is employed and complemented by quasi-classical trajectory calculations. Rate coefficients for ortho-H2 are provided for the first time. Hyperfine resolved rate coefficients are also deduced. Collisional propensity rules are discussed and comparisons between quantum and classical rate coefficients are presented. This collisional data should prove useful in interpreting HC3N observations in the cold and warm ISM, as well as in protoplanetary disks.