Infrared diode laser spectra of MgH and MgD (<i>X</i> 2Σ+)

Abstract

Infrared absorption spectra of magnesium hydride in its 2Σ+ ground state have been measured at Doppler limited resolution in a dc discharge of hydrogen over magnesium. Most of the transitions arise from the fundamental bands of 24MgH and 24MgD, but, in addition, a few lines attributable to 25Mg and 26Mg species have been detected, as well as v=2←1 hot band transitions in 24MgH and 24MgD. Most of the lines are characterized by a doublet splitting due to the electron spin–rotation interaction (γN⋅S) which helps to distinguish them from the broader Rydberg transitions of atomic magnesium observed in the same spectral region. The spectra were analyzed in a combined fit with the FIR pure rotational transitions which leads to an accurate set of molecular parameters either for each vibrational level or as Dunham coefficients. The mass dependence of the molecular parameters is examined in terms of possible breakdown of the Born–Oppenheimer approximation.