Revisiting the Discrepancy between Experimental and Theoretical Predictions of the Adiabaticity of Ti + CHOH.

We revisit the naked transition metal cation (Ti) and methanol reaction and go beyond the standard Landau-Zener (LZ) picture when modeling the intersystem crossing (ISC) rate between the lowest doublet and quartet states. We use both (i) unconstrained Born-Oppenheimer molecular dynamics (BOMD) calculations with an approximate two-state method to estimate population transfer between spin diabats and (ii) constrained dynamics to explore energetically accessible portions of the - 1 crossing seam, where is the total number of internal degrees of freedom. Whereas previous LZ calculations (that necessarily relied on the Condon approximation to be valid) fell short and predicted much slower crossing probabilities than shown in experiment, we show that ISC can occur rapidly because the spin-orbit coupling (SOC) between the doublet and quartet surfaces can vary by 2 orders of magnitude (depending on where in the seam the crossing occurs during dynamics) and the crossing region is revisited multiple times during a dynamics run of a few hundred femtoseconds.

Dissociative electron attachment and Ar+ reaction with chromium hexacarbonyl, 296-400 K.

Dissociative electron attachment rate constants have been measured for Cr(CO)6 under thermal conditions, 296-400 K, yielding Cr(CO)5- product. At 296 K, 2.92 ± 0.

Intersystem Crossing Control of the Nb + CO → NbO + CO Reaction.

The transfer of an oxygen atom from carbon dioxide (CO) to a transition metal cation in the gas phase offers atomic level insights into single-atom catalysis for CO activation. Given that these reactions often involve open-shell transition metals, they may proceed through intersystem crossing between different spin manifolds. However, a definitive understanding of such spin-forbidden reaction requires dynamical calculations on multiple global potential energy surfaces (PESs) coupled by spin-orbit couplings.

A Common Bottleneck for Metal Oxidation by Molecular Oxygen Across Size Regimes: Kinetics of Atomic Lanthanide Cations (La-Lu) with O.

Kinetics of the lanthanide cations (Ln = La-Lu excluding ) reacting with molecular oxygen were measured in a selected-ion flow tube apparatus from 300 to 600 K. Where exothermic, these reactions occur efficiently, producing LnO + O. The reactions display positive temperature dependences consistent with Arrhenius equation behavior and show small activation energies (0-2 kJ mol) that are strongly correlated to promotion energies of the Ln atoms.

Multistate Dynamics and Kinetics of CO Activation by Ta in the Gas Phase: Insights into Single-Atom Catalysis.

The activation of carbon dioxide (CO) by a transition-metal cation in the gas phase is a unique model system for understanding single-atom catalysis. The mechanism of such reactions is often attributed to a "two-state reactivity" model in which the high-energy barrier of a spin state correlating with ground-state reactants is avoided by intersystem crossing (ISC) to a different spin state with a lower barrier. However, such a "spin-forbidden" mechanism, along with the corresponding dynamics, has seldom been rigorously examined theoretically, due to the lack of global potential energy surfaces (PESs).