Infrared photodissociation spectroscopy of [formula omitted] ( n = 3 and 4) by using free electron laser

Abstract

Photodissociation spectra of NH 4 + ( NH 3 ) n were measured for n = 3 and 4 in the range of 1070–1680 cm −1 by using an infrared free electron laser. Three vibrational bands observed for each species are assigned to the intramolecular vibrational modes: the ν 2 and ν 4 modes of NH 3 and the ν 4 mode of NH 4 + . When the first solvation shell is completed at n = 4, the ν 2(NH 3) and ν 4 ( NH 4 + ) wavenumbers are found to be higher by 182 and 36 cm −1, respectively, than those in free molecules, whereas the ν 4(NH 3) wavenumber is lower by 29 cm −1.