Anharmonic densities of states: A general dynamics-based solution

Electron Binding Energy Spectra of AlnPt- Clusters─A Combined Experimental and Computational Study

Results of size-selected electron photo-detachment experiments and density functional theory calculations on anionic Al_nPt^-, n = 1-7, clusters are presented and analyzed. The measured and calculated spectra of electron binding energies are, overall, in excellent accord with each other. The analysis reveals the general importance of accounting for the multiplicity of structural forms of a given-size cluster that can contribute to its measured spectrum, especially when the clusters are fluxional and/or the conditions of the experiment allow for structural transitions. We show that for the systems studied here, the size-specific peculiarities of the measured spectra can be understood in terms of the combined contributions of corresponding different accessible stable equilibrium conformations, bona-fide transition-state configurations, and electronic-crossing structures that may play the role of effective barriers in electronically nonadiabatic dynamics.

Modeling Gas-Phase Unimolecular Dissociation for Bond Dissociation Energies: Comparison of Statistical Rate Models within RRKM Theory

The Rice-Ramsperger-Kassel-Marcus (RRKM) theory provides a simple yet powerful rate theory for calculating microcanonical rate constants. In particular, it has found widespread use in combination with gas-phase kinetic experiments of unimolecular dissociations to extract experimental bond dissociation energies (BDEs). We have previously found several discrepancies between the computed BDE values and the respective experimental ones, obtained with our empirical rate model, named L-CID. To investigate the reliability of our rate model, we conducted a theoretical analysis and comparison of the performance of conventional rate models and L-CID within the RRKM framework. Using the previously published microcanonical rate data as well as reaction cross-section data, we show that the BDE values obtained with the L-CID model agree with the ones from the other rate models within the expected uncertainty bounds. Based on this agreement, we discuss the possible rationalization of the good performance of the L-CID model.