The full infrared spectrum of molecular hydrogen

TL;DR

This paper predicts the complete infrared spectrum of molecular hydrogen with unprecedented accuracy by incorporating recent ab initio calculations, including electric quadrupole and magnetic dipole transitions, enhancing understanding of hydrogen's spectral emissions.

Contribution

It provides the first detailed computation of hydrogen's full infrared spectrum, including both electric quadrupole and magnetic dipole transitions, with improved accuracy over previous models.

Findings

Magnetic dipole transitions significantly increase emission probabilities for high rotational levels.

The study derives the total radiative lifetime of each rovibrational state.

The computed spectrum covers the 3-20 μm range with high precision.

Abstract

The high spectral resolution R about 45,000 provided by IGRINS (Immersion Grating INfrared Spectrometer) at MacDonald Observatory and R 100,000 achieved by CRIRES (CRyogenic high-resolution InfraRed Echelle Spectrograph) at VLT (Very Large Telescope) challenges the present knowledge of infrared spectra. aims We aim to predict the full infrared spectrum of molecular hydrogen at a comparable accuracy. methods We take advantage of the recent theoretical ab initio studies on molecular hydrogen to compute both the electric quadrupole and magnetic dipole transitions taking place within the ground electronic molecular state of hydrogen. results We computed the full infrared spectrum of molecular hydrogen at an unprecedented accuracy and derive for the first time the emission probabilities including both electric quadrupole ($\Delta J = 0, \pm$2) and magnetic dipole transitions ($\Delta J = 0$) as well as the total radiative lifetime of each rovibrational state. Inclusion of magnetic dipole transitions increases the emission probabilities by factors of a few for highly excited rotational levels, which occur in the 3-20 $\mu$ range}