Full Spectroscopic Model and Trihybrid Experimental-Perturbative-Variational Line List for CN

TL;DR

This paper develops a comprehensive spectroscopic model and hybrid line list for CN, combining experimental, perturbative, and variational data, enabling detailed analysis of CN's spectral properties and its potential as a probe for fundamental constant variations.

Contribution

A novel trihybrid energy spectroscopic model and line list for CN, integrating experimental, perturbative, and variational approaches, with detailed energy levels and transitions.

Findings

28,004 energy levels for CN and isotopologues

Over 2.2 million spectral transitions up to 60,000 cm-1

No highly sensitive transitions for proton-to-electron mass ratio variation found

Abstract

Accurate line lists are important for the description of the spectroscopic nature of small molecules. While a line list for CN (an important molecule for chemistry and astrophysics) exists, no underlying energy spectroscopic model has been published, which is required to consider the sensitivity of transitions to a variation of the proton-to-electron mass ratio. Here we have developed a Duo energy spectroscopic model as well as a novel hybrid style line list for CN and its isotopologues, combining energy levels that are derived experimentally (Marvel), using the traditional/perturbative approach (Mollist), and the variational approach (from a Duo spectroscopic model using standard ExoMol methodology). The final Trihybrid ExoMol-style line list for 12C14N consists of 28,004 energy levels (6,864 experimental, 1,574 perturbative, the rest variational) and 2,285,103 transitions up to 60,000 cm-1 between the three lowest electronic states (X2Sigma+, A2Pi and B2Sigma+). The spectroscopic model created is used to evaluate CN as a molecular probe to constrain the variation of the proton-to-electron mass ratio; no overly promising sensitive transitions for extragalactic study were identified.