Spectra of NH3 in He droplets in the 3 μm range

Depletion spectra of the ν1, ν3, and 2ν4 vibrational bands (ν = 3000-3500 cm−1) of ammonia molecules embedded in He droplets have been studied. The effective rotational constants of ammonia in helium BHe and CHe are found to be about 5% smaller than those of free NH3. The magnitude of the inversion splitting is very close (within 6%) to that in the free molecule. Relaxation times of different rotational levels in the studied vibrationally excited states are estimated to be in the range of 1 × 10−12-5 × 10−11 s and are found to have strong dependence on the rotational quantum numbers.