Visible photodissociation spectra of gaseous rhodamine ions: Effects of temperature and tagging

Abstract

This paper reports on the effect of He, Ar, and N2 tagging on visible photodissociation (VisPD) spectra of Rhodamine 123 ions. We show that the effect of tagging on the determination of the 0–0 transition in the electronic spectra is negligible. In contrast to the photodissociation spectra of the bare ions, the tagging method provides resolved Franck-Condon envelopes. Ar and N2 tagging spectra revealed minor blue-shifts (∼ 0.5nm) for some maxima in the Franck-Condon envelope with respect to the He tagging spectrum. The N2 tagging VisPD spectrum was less resolved compared to He and Ar tagging spectra. Further, we have investigated the effect of temperature on photodissociation spectra of bare rhodamine ions. At room temperature, the absorption spectrum is dominated by the absorption of vibrationally excited ions. Vibrationally relaxed ions start to be dominantly sampled at about 150K. In average, three to four photons are required to induce photodissociation of the rhodamine ions and it is slightly wavelength dependent. We ascribe it to the fluorescence process.