Experimental and theoretical investigation on N2 pressure-induced coefficients of the lowest rotational transitions of HCN

TL;DR

This study combines experimental measurements and computational methods to determine pressure broadening and shift coefficients of HCN's rotational lines, enhancing spectroscopic data for atmospheric modeling.

Contribution

It introduces a validated, low-cost computational approach for HCN-N2 interactions and extends the dataset to higher rotational transitions with temperature dependence.

Findings

First experimental data for N2 pressure broadening of HCN lines

Validated computational method accurately predicts line-shape parameters

Extended dataset supports atmospheric modeling of HCN in Earth and Titan environments

Abstract

We present the first experimental determination of room-temperature N2 pressure broadening, speed dependent broadening, and pressure shift coefficients of the three lowest rotational lines of HCN. The experimental results served to assess the accuracy of a low-cost yet accurate computational strategy, which relies on a simplified characterization of the HCN-N2 interaction potential, and employs a novel approximate method of solving the quantum scattering problem. Building on the validation of this computational approach, the dataset was extended to higher rotational transitions, up to J(HCN)=5-4. For these transitions, we provide the temperature dependence of the pressure broadening coefficient, its speed dependence parameter, and the Dicke narrowing parameter. This new dataset can support and refine the modeling of HCN in both the terrestrial and Titan's atmospheres. This work constitutes an important step towards populating spectroscopic databases with accurate HCN line-shape parameters.