Emission Spectroscopy of AlH: the X¹Σ⁺, A¹Π and C¹Σ⁺ States Characteristics

Abstract

The visible spectrum of AlH has been investigated at high resolution between 20000 and 21500 cm -1 using a conventional spectroscopic technique. The AlH molecules were formed and excited in an aluminium hollow-cathode lamp with two anodes, filled with a mixture of Ne carried gas and a trace of NH 3 . The emission from the discharge was observed with a plane grating spectrograph and recorded by a photomultiplier tube. The 0-0 and 1-1 bands of the C 1 + -A 1 system and 0-2 band of the A 1 -X 1 + were identified at 21126, 21368 and 20276 cm -1 , respectively. In total 121 transition wave numbers belonging to three bands were precisely measured (with accuracy of 0.003 cm -1 ) and rotationally analysed. The new data were elaborated with the help of recent X 1 + state parameters reported by White et al. and of the C 1 + , A 1 states constants reported by Szajna and Zachwieja. As a result of this merged analysis the set of the molecular parameters and rotational terms values for the three lower lying states of the AlH molecule have been significantly improved.