Resonant twohyphen;photon ionization of fluorene rarehyphen;gas van der Waals complexes

摘要

Resonant twohyphen;photon ionization combined with timehyphen;ofhyphen;flight mass spectrometry was applied for the interrogation of theS0thinsp;rarr;thinsp;S1electronichyphen;vibrational excitations of van der Waals complexes of fluorene (FL) with rarehyphen;gas atoms and N2in supersonic jets. Energyhyphen;resolved and masshyphen;resolved spectra of FLthinsp;sdot;thinsp;Ne, FLthinsp;sdot;thinsp;Arn(n=1ndash;3), FLthinsp;sdot;thinsp;Kr, FLthinsp;sdot;thinsp;Xe, and FLthinsp;sdot;thinsp;N2were recorded over the energy range 0ndash;800 cmminus;1above the electronic origin ofS1. The red microscopic spectral shifts of the electronic origins of FLthinsp;sdot;thinsp;R (R=Ar,thinsp;Kr, and Xe) complexes are dominated by dispersive interactions, being proportional to the polarizability of R. The vibrational level structure of FLthinsp;sdot;thinsp;Rn(R=Ar,thinsp;Kr, and Xe) complexes exhibits intramolecular vibrational excitations of FL, as well as intermolecular vibrations, which involve the relative motion of FL and R in the complex. The spectra of FLthinsp;sdot;thinsp;Ne and FLthinsp;sdot;thinsp;N2reveal a rich vibrational structure in the vicinity of the electronic origin, indicating a substantial change of the nuclear configuration upon electronic excitation. Upper and lower bounds on the dissociation energies of FLthinsp;sdot;thinsp;R (R=Ne,thinsp;Kr, and Xe) and FLthinsp;sdot;thinsp;Ar2were inferred from the vibrational level structure in the masshyphen;resolved spectra, where the disappearance of the signal of the parent van der Waals ion and the appearance of the ion signal of the fragments mark the onset of the vibrational predissociation process.