Line strengths of rovibrational and rotational transitions within the X³Σ⁻ ground state of NH

James S A Brooke; Peter F Bernath; Colin M Western; Marc C van Hemert; Gerrit C Groenenboom

doi:10.1063/1.4891468

Line strengths of rovibrational and rotational transitions within the X³Σ⁻ ground state of NH

J Chem Phys. 2014 Aug 7;141(5):054310. doi: 10.1063/1.4891468.

Authors

James S A Brooke¹, Peter F Bernath¹, Colin M Western², Marc C van Hemert³, Gerrit C Groenenboom⁴

Affiliations

¹ Department of Chemistry, University of York, York YO10 5DD, United Kingdom.
² School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, United Kingdom.
³ Faculty of Science, Leiden Institute of Chemistry, Theoretical Chemistry, Gorlaeus Laboratories, Einsteinweg 55, 2333 CC Leiden, The Netherlands.
⁴ Theoretical Chemistry, Institute for Molecules and Materials (IMM), Radboud University Nijmegen, Heyendaalseweg 135, 6525 AJ Nijmegen, The Netherlands.

PMID: 25106590
DOI: 10.1063/1.4891468

Abstract

A new line list for rovibrational and rotational transitions, including fine structure, within the NH X³Σ⁻ ground state has been created. It contains line intensities in the form of Einstein A and f-values, for all possible bands up to v' = 6, and for J up to between 25 and 44. The intensities are based on a new dipole moment function (DMF), which has been calculated using the internally contracted multi-reference configuration interaction method with an aug-cc-pV6Z basis set. The programs RKR1, LEVEL, and PGOPHER were used to calculate line positions and intensities using the most recent spectroscopic line position observations and the new DMF, including the rotational dependence on the matrix elements. The Hund's case (b) matrix elements from the LEVEL output (available as Supplement 1 of the supplementary material) have been transformed to the case (a) form required by PGOPHER. New relative intensities for the (1,0) band have been measured, and the calculated and observed Herman-Wallis effects are compared, showing good agreement. The line list (see Supplement 5 of the supplementary material) will be useful for the study of NH in astronomy, cold and ultracold molecular systems, and in the nitrogen chemistry of combustion.