Nonlinear effects in infrared action spectroscopy of silicon and vanadium oxide clusters: experiment and kinetic modeling

Abstract

For structural assignment of gas phase compounds, infrared action spectra are usually compared to computed linear absorption spectra. However, action spectroscopy is highly nonlinear owing to the necessary transfer of the excitation energy and its subsequent redistribution leading to statistical ionization or dissociation. Here, we examine by joint experiment and dedicated modeling how such nonlinear effects affect the spectroscopic features in the case of selected inorganic clusters. Vibrational spectra of neutral silicon clusters are recorded by tunable IR-UV two-color ionization while IR spectra for cationic vanadium oxide clusters are obtained by IR multiphoton absorption followed by dissociation of the bare cluster or of its complex with Xe. Our kinetic modeling accounts for vibrational anharmonicities, for the laser interaction through photon absorption and stimulated emission rates, as well as for the relevant ionization or dissociation rates, all based on input parameters from quantum on the average number of photons absorbed, which is otherwise unaccessible information: several to several tens of photons need to be absorbed to observe a band through dissociation, while three to five photons can be sufficient for detection of a band via IR-UV ionization.

The repopulation of electronic states upon vibrational excitation of niobium carbide clusters

“…A better estimate for the internal energy of a cluster as a function of the IR pulse energy could be obtained by solving a set of coupled excitation rate equations 39,40 which in our case can not be done due to the lack of information about absorption properties and the anharmonicity parameters for NbC clusters. Such a model is thus outside the scope of the current work.…”

Geometric Structures and Magnetic Interactions in Small Chromium Oxide Clusters

“…The main reasons here for are the multiple photon aspect and the statistical dissociation of the cluster-rare gas complexes in the experiment, which are not included in the computations. A detailed discussion of the consequences of those effects can be found in ref 40…”

The Impact of the Vanadium Oxide Addition on the Physicochemical Performance Stability and Intercalation of Lithium Ions of the TiO2-rGO-electrode in Lithium Ion Batteries

“…The fundamental vibrations in all of the TiO2-based composites appear in the FTIR spectra as a very intense broad band, ascribed to stretching vibrations of Ti-O bonds (550-653 cm −1 ) [16,17]. The next band is visible at 1103 cm −1 , and according to the literature [18] is related to stretching vibrations of unshared V=O bonds [19]. The highest intensity of this band is observed for the sample obtained with the highest quantity of vanadium precursor.…”