Quantum cascade laser absorption spectroscopy of the band of deuterium bromide at 5 μm

The invention, and subsequent development of external cavity quantum cascade lasers (EC-QCLs) has allowed relatively simple access to a wide spectral region for high resolution laser spectroscopy. In this Letter, we demonstrate the application of a broadly tunable 5.3 μm EC-QCL to absorption spectroscopy on the fundamental band of deuterium bromide. The large tuning range is utilised to record spectra allowing the hyperfine coupling constants to be determined for the v = 0 and v = 1 levels of both D79Br and D81Br. We present the first measurement to our knowledge of e 2 Qq ( v = 1 ) for D81Br, given a value of 460.5 ± 12 MHz.