# The rotational excitation of HCN and HNC by He: new insights on the HCN/HNC abundance ratio in molecular clouds

@article{Sarrasin2010TheRE, title={The rotational excitation of HCN and HNC by He: new insights on the HCN/HNC abundance ratio in molecular clouds}, author={E. Sarrasin and Dahmani Abdallah and Michael Wernli and A. Faure and Jos{\'e} Cernicharo and F. Lique}, journal={Monthly Notices of the Royal Astronomical Society}, year={2010}, volume={404}, pages={518-526} }

Modelling of molecular emission from interstellar clouds requires the calculation of rates for excitation by collisions with the most abundant species. The present paper focuses on the calculation of rate coefficients for rotational excitation of the hydrogen cyanide (HCN) and hydrogen isocyanide (HNC) molecules in their ground vibrational state in collision with He. The calculations are based on new two-dimensional potential energy surfaces obtained from highly correlated ab initio…

## 80 Citations

### The rotational excitation of HCN and HNC by He: temperature dependence of the collisional rate coefficients

- Physics
- 2010

Modelling of molecular emission from interstellar clouds requires the calculation of rates for excitation by collisions with the most abundant species. This paper deals with the calculation of rate…

### Hyperfine excitation of HCN by H2 at low temperature

- Physics
- 2012

Modelling of molecular emission spectra from interstellar clouds requires the calculation of rate coefficients for (de-)excitation by collisions with the most abundant species. We calculate rate…

### Collisional excitation of interstellar HCl by He

- Physics
- 2012

Modelling of molecular emission from interstellar clouds requires the calculation of rate coefficients for excitation by collisions with the most abundant species. This paper deals with the…

### The Photodissociation of HCN and HNC: Effects on the HNC/HCN Abundance Ratio in the Interstellar Medium.

- PhysicsThe Astrophysical journal
- 2017

To properly describe the HNC/HCN abundance ratio in astronomical environments illuminated by an intense ultraviolet radiation field it is necessary to use different photodissociation rates for each of the two isomers, obtained by integrating the product of the photodISSociation cross sections and ultraviolet Radiation field over the relevant wavelength range.

### The rotational excitation of the interstellar HNC by para- and ortho-H2.

- Physics, ChemistryPhysical chemistry chemical physics : PCCP
- 2011

A new four dimensional (4D) potential energy surface for the HNC-H(2) collisional system is presented and it is expected that they will help to solve the interstellar problem of relative abundance of the HCN and HNC isomers.

### Rotational (de-)excitation of isocyanogen by collision with helium at low energies.

- PhysicsThe Journal of chemical physics
- 2018

The cross sections for the rotational (de-)excitation of CNCN after a collision by He up to 2000 cm-1 total energies are obtained and these cross sections are used to deduce the collision rates in the 10-300 K range.

### Collisional excitation of HNC by He found to be stronger than for structural isomer HCN in experiments at the low temperatures of interstellar space

- PhysicsNature Chemistry
- 2022

HCN and its unstable isomer HNC are widely observed throughout the interstellar medium, with the HNC/HCN abundance ratio correlating strongly with temperature. In very cold environments HNC can even…

### Rotational excitation of HCN by para- and ortho-H₂.

- PhysicsThe Journal of chemical physics
- 2014

New rate coefficients will be crucial to improve the estimation of the HCN abundance in the interstellar medium and were compared with previously published HCN-para-H2(j = 0) rate coefficients.

### Isomerism Effects in the Collisional Excitation of Cyanoacetylene by Molecular Hydrogen

- Physics, ChemistryACS Earth and Space Chemistry
- 2019

Rotational excitation of the interstellar HC2NC and HNC3 molecules, two isomers of HC3N, induced by collisions with H2 is investigated at low collision energy using a quantum time-independent…

### Revised study of the collisional excitation of HCO+ by H2(j = 0)

- Chemistry, Physics
- 2014

Rotational excitation of the interstellar HCO + by para-H 2 ( j = 0) is investigated. The scattering calculations are based on a new potential energy surface (PES) for the HCO + –H 2 van der Waals…

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