Intrinsic fluorescence properties of rhodamine cations in gas-phase: triplet lifetimes and dispersed fluorescence spectra

Abstract

We have investigated the gas phase triplet state lifetimes and dispersed fluorescence spectra of several types of rhodamine cations confined in a quadrupole ion trap and thermalized to 85 K. The measured triplet lifetimes of rhodamine cations Rh6G⁺, Rh575⁺, RhB⁺, and Rh101⁺ are found to be on the order of seconds, several orders of magnitude longer than those typically observed for the same dyes in optical condensed phase measurements. In addition dispersed fluorescence emission spectra in the gas phase at 85 K have been measured. The experimental gas phase results as well as solution measurements are compared to density functional calculations and the previous literature. Possible explanations for the discrepancy of gas and solution phase triplet lifetimes are discussed.