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Laser-induced- and dispersed-fluorescence studies of rhodamine 590 and 640 ions formed by electrospray ionization: Observation of fluorescence from highly-excited vibrational levels of S1 states

Abstract

The laser-induced fluorescence (LIF) and dispersed fluorescence (DF) spectra of two rhodamine dye cations, rhodamine 590 (R590) and rhodamine 640 (R640), were measured under isolated gas-phase condition. The ions were generated by an electrospray ion source and desolvated ions were accumulated in a room temperature quadrupole ion-trap. For R590, three LIF bands were observed in the visible and ultraviolet region. The visible band is the same as that previously observed and the other two bands of R590 are newly observed in the ultraviolet region. For both dyes, the LIF and DF spectra in the visible region were assigned to the S1 - S0 transition, and appeared at higher energy compared with those in the methanol solution. These solvent shifts suggest that the S1 state is preferentially stabilized by the interaction with methanol molecules in both dyes. The DF spectra observed by the uv excitation for both dyes were similar to those of the visible excitation, except for the red-shifts of the peak wavelengths, and assigned to the S1 - S0 transition. These shifts are explained by the emission from the highly excited vibrational levels of the S1 state. Because of the lack of the vibrational relaxation in the gas-phase, the vibrationally excited S1 states formed by the fast internal conversion from higher electronic states survive to emit the fluorescence.

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Publication details

The article was received on 27 Jun 2018, accepted on 03 Oct 2018 and first published on 03 Oct 2018


Article type: Paper
DOI: 10.1039/C8CP04067B
Citation: Phys. Chem. Chem. Phys., 2018, Accepted Manuscript
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    Laser-induced- and dispersed-fluorescence studies of rhodamine 590 and 640 ions formed by electrospray ionization: Observation of fluorescence from highly-excited vibrational levels of S1 states

    K. Honma, Phys. Chem. Chem. Phys., 2018, Accepted Manuscript , DOI: 10.1039/C8CP04067B

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