The relaxation from linear to triangular Ag3 probed by femtosecond resonant two-photon ionization

Abstract

We present extended NeNePo (negative to neutral to positive) measurements on the ultrafast dynamics in the ground state of neutral, mass-selected Ag3 molecules. A vibrational wave packet in the neutral molecule is created with an ultrashort laser pulse by photodetachment of the excess electron from the corresponding mass-selected anion. The subsequent molecular rearrangement is probed by photoionization after a selected time delay. Complementary to our previous investigations of this process, we now use two-photon photoionization via a resonant state in the probe step. Here, a bound–bound excitation to a well-known state followed by one-photon ionization is used instead of the nonresonant bound/free transition into the ionic continuum. Using radiation with wavelengths near 370 nm for resonant ionization, we observe a fast bending motion of the initially linear Ag3, followed by an ultrafast intramolecular vibrational energy redistribution, interpretable as an intramolecular collision process. The signal shows an apparent loss of vibrational coherence after the collision, which can be explained by the finite temperature of the anionic clusters in our experiment. Additionally, we describe a previously unknown resonance in the linear neutral molecule around 500 nm.