Nonequilibrium effects of cavity leakage and vibrational dissipation in thermally activated polariton chemistry

Abstract

In vibrational strong coupling (VSC), molecular vibrations strongly interact with the modes of an optical cavity to form hybrid light–matter states known as vibrational polaritons. Experiments show that the kinetics of thermally activated chemical reactions can be modified by VSC. Transition-state theory, which assumes that internal thermalization is fast compared to reactive transitions, has been unable to explain the observed findings. Here, we carry out kinetic simulations to understand how dissipative processes, namely, those introduced by VSC to the chemical system, affect reactions where internal thermalization and reactive transitions occur on similar timescales. Using the Marcus–Levich–Jortner type of electron transfer as a model reaction, we show that such dissipation can change reactivity by accelerating internal thermalization, thereby suppressing nonequilibrium effects that occur in the reaction outside the cavity. This phenomenon is attributed mainly to cavity decay (i.e., photon leakage), but a supporting role is played by the relaxation between polaritons and dark states. When nonequilibrium effects are already suppressed in the bare reaction (the reactive species are essentially at internal thermal equilibrium throughout the reaction), we find that reactivity does not change significantly under VSC. Connections are made between our results and experimental observations.

Inherent Promotion of Ionic Conductivity via Coherent Vibrational Strong Coupling of Water

“…[1][2][3] On one hand, electronic excitation of energy states of molecules are coupled to the electromagnetic fields and giving the unusual photochemical dynamics 4,5 or coherent electronic transport. [6][7][8] On the other hand, vibrational level of molecules can be coupled to the vacuum fields of optical cavity for the formation of vibrational strong coupling state, [9][10][11][12] leading to the modification of chemical landscapes for the reactivity modulation. [13][14][15][16] That is related to the classical concept of "vibrational excitation for bond-selective chemical reactions" 17 even without light pumping.…”

Inherent Promotion of Ionic Conductivity via Coherent Vibrational Strong Coupling of Water

“…72−75 We may expect that the contribution of the dark states could act as an energy reservoir to extend the coherence to modification of the proton transfer rate as well as increase the dielectric constants. 62,63,76,77 The modification of the responses of molecular systems under the perturbations requires novel theoretical consideration for further quantitative descriptions about the present observation.…”

Polariton relaxation under vibrational strong coupling: Comparing cavity molecular dynamics simulations against Fermi's golden rule rate

“…From an experimental point of view, there has been an extensive exploration of VSC catalytic effects in different types of chemical reactions [14][15][16][17][18][19][20] and the use of VSC to alter other molecular properties in the absence of an external laser pumping 21 has also been investigated; at the same time, spectroscopists have also focused on the ultrafast dynamics of vibrational polaritons by pump-probe 22,23 and two-dimensional infrared (IR) [24][25][26][27][28][29] spectroscopies. From a theoretical point of view, while the detailed mechanism of "VSC catalysis" is still not well understood [30][31][32][33][34][35][36][37][38] , the current models of ultrafast polariton dynamics appear to be largely consistent with observations [39][40][41][42][43][44][45] . a) Electronic mail: taoli@sas.upenn.edu b) Electronic mail: anitzan@sas.upenn.edu c) Electronic mail: subotnik@sas.upenn.edu…”