# MARVEL analysis of the measured high-resolution spectra of $^{14}$NH

## TL;DR

This paper uses the MARVEL technique to analyze high-resolution spectra of $^{14}$NH, determining rovibronic energy levels across four electronic states by compiling and validating over 3000 spectral transitions from various sources.

## Contribution

It provides a comprehensive, experimentally validated set of rovibronic energy levels for $^{14}$NH using the MARVEL method, including a detailed spectroscopic network and insights into electronic structure calculations.

## Key findings

- Most transitions form a single consistent spectroscopic network
- Determined 1058 energy levels across four electronic states
- CCSD(T) method poorly predicts the ext{a} state excitation energy

## Abstract

Rovibronic energy levels are determined for four low-lying electronic states (\X, \A, \Sa, and \Sc) of the imidogen free radical ($^{14}$NH) using the \Marvel\ (Measured Active Rotational-Vibrational Energy Levels) technique. Compilation of transitions from both laboratory measurements and solar spectra, found in 18 publications, yields a dataset of 3002 rovibronic transitions forming elements of a measured spectroscopic network (SN). At the end of the MARVEL procedure, the majority of the transitions form a single, self-consistent SN component of 2954 rovibronic transitions and 1058 energy levels, \NoX, \NoA, and \Noc\ for the \X, \A, and \Sc\ electronic states, respectively. The \Sa\ electronic state is characterized by \Noa\ $\Lambda$-doublet levels, counting each level only once. Electronic structure computations show that unusually the CCSD(T) method does not accurately predict the \Sa\ excitation energy even at the complete basis set limit.