Structure of Pro4H+ investigated by infrared photodissociation (IRPD) spectroscopy and theoretical calculations

Combining with electrospray ionization (ESI) mass spectrometry, infrared photodissociation (IRPD) spectroscopy is a powerful method to study structures of cluster ions in the gas phase. In this paper, infrared photodissociation spectrum of Pro4H+ in the range of 2700–3600 cm−1 was obtained experimentally. Both theoretically predicted spectra of the two most stable isomers of Pro4-1 and Pro4-2 obtained at the level of M062X/6-31 + G(d, p) are in good consistent with the experimental results. The two isomers have similar structures and close energies. Both of them only consist of zwitterionic units, indicating the strong salt-bridged interactions inside the clusters. And the calculated collision cross section (ccs) of Pro4-1 is found to be very close to the experimental result previously reported.

IRPD Spectroscopy of Pro4H+ was obtained in the gas phase and studied by theoretical calculations.Figure optionsDownload as PowerPoint slide