Femtosecond Dynamics of Linear Ag₃

Abstract

A femtosecond negative ion−neutral−positive ion charge reversal apparatus has been developed, following the concept of Wöste and Berry, to carry out spectroscopy of transient neutral species along the reaction coordinate. We report studies of the ultrafast dynamics of linear Ag3 produced by photodetachment of linear Ag3 -. The background-free time-resolved multiphoton ionization spectra of Ag3 taken at various wavelengths show a strong probe time and wavelength dependence, indicating important roles both of an intermediate state resonance and the ionization detection window in the time-resolved ionization signal. Based on these results, we speculate on the wavepacket dynamics along the coordinate of the linear-to-triangular rearrangement on the ground state potential energy surface.

Regular and irregular vibrational states: Localized anharmonic modes and transition-state spectroscopy of Na3

“…The most promising experiments for quartet Na 3 are laser-induced fluorescence or stimulatedemission pumping, ideally from an excited quartet state with a linear equilibrium geometry, or photodetachment from a linear state of the triplet Na 3 Ϫ ion. Such a photodetachment scheme has already been implemented for doublet Ag 3 , [27][28][29] although in that case the density of states at the energy of the barrier is very high. Other trimers, such as Li 3 and K 3 , may be better candidates.…”

Femtosecond Time‐Resolved Geometry Relaxation and Ultrafast Intramolecular Energy Redistribution in Ag2Au

“…In fact, such two-photon selective NeNePo probing by resonant excited neutral states has been reported in the case of Ag 3 . [12,18,19] If the transient signal of Ag 2 Au at 350 nm is indeed a result of a resonant two-photon ionization process, in contrast to ionization at 406 nm, the relative intensity of the 350 nm signal should be much higher than that of the 406 nm signal. However, the signal intensities at 350 and 406 nm probing are comparable, [29] and thus resonant two-photon ioniza- tion can be ruled out and the prevalence of a favorable Franck-Condon window is likely to be the origin of the observed signal for Ag 2 Au at E pr2ph = 7.1 eV.…”

“…[10] In the case of Ag 3 , the relaxation dynamics include sequential processes of configurational relaxation to the triangular structure ( 2 B 2 state), intracluster collisions, and IVR. [5,7,8,[11][12][13] The process of IVR in an isolated molecule or cluster involves vibrational energy flow from an initially excited vibrational mode, or a wave packet of such vibrational modes, to other types of nuclear motion. [14] IVR is the manifestation of quantum coherence imposed by the preparation process on the initial state.…”

The Transition State of Thermal Organic Reactions: Direct Observation in Real Time

“…Combining the femtosecond time resolution and negative-ion-beam techniques provides a unique way to study the nuclear motions of neutral molecules in the electronic ground state, and this has been successful for Ag 3 and Ag 4 . [3][4][5][6][7] For stable (positive electron affinity) negative ions prepared in the gas phase the electronic states are lower in energy than the neutral ground state. Thus, the ground state of the neutral reaction can be prepared with well-defined nuclear configuration (coherent wave packet) by photodetaching the electron from the anion with a femtosecond laser pulse.…”

“…Numerous examples of femtochemistry studies have been reported for reactions on excited surfaces and in all phases of matter (see, for example, recent references [1] and [2]). Combining the femtosecond time resolution and negative-ion-beam techniques provides a unique way to study the nuclear motions of neutral molecules in the electronic ground state, and this has been successful for Ag 3 and Ag 4 . [3][4][5][6][7] For stable (positive electron affinity) negative ions prepared in the gas phase the electronic states are lower in energy than the neutral ground state.…”