Observation of the fine structure for rovibronic spectral lines in visible part of emission spectra of $D_2$

TL;DR

This paper reports the first observation of fine structure in the visible emission spectrum of D2, revealing pseudo doublets caused by triplet splitting, which can aid in identifying unassigned spectral lines of the molecule.

Contribution

It introduces the first observation of fine structure in D2's visible emission spectrum and proposes using this for spectral line identification.

Findings

Observed pseudo doublets with 0.2 cm$^{-1}$ splitting

Attributed the doublets to triplet splitting in lower rovibronic levels

Suggested application for identifying unassigned spectral lines

Abstract

For the first time in visible part of the $D_2$ emission spectrum the pseudo doublets representing partly resolved fine structure of rovibronic lines have been observed. They are characterized by splitting values about 0.2 cm$^{-1}$ and relative intensity of the doublet components close to 2.0. It is shown that they are determined by triplet splitting in lower rovibronic levels of various $^3\Lambda_g^\pm \to c^3\Pi_u^-$ electronic transitions. It is proposed to use an existence of such partly resolved fine structure patterns for identification of numerous unassigned spectral lines of the $D_2$ molecule coming from great variety of triplet "gerade" electronic states to vibro-rotational levels of the $c^3\Pi_u^-$ state.