Electric Fields Influence Intramolecular Vibrational Energy Relaxation and Line Widths

Abstract

Intramolecular vibrational energy relaxation (IVR) is fundamentally important to chemical dynamics. We show that externally applied electric fields affect IVR and vibrational line widths by changing the anharmonic couplings and frequency detunings between modes. We demonstrate this effect in benzonitrile for which prior experimental results show a decrease in vibrational line width as a function of applied electric field. We identify three major channels for IVR that depend on electric field. In the dominant channel, the electric field affects the frequency detuning, while in the other two channels, variation of anharmonic couplings as a function of field is the underlying mechanism. Consistent with experimental results, we show that the combination of all channels gives rise to reduced line widths with increasing electric field in benzonitrile. Our results are relevant for controlling IVR with external or internal fields and for gaining a more complete interpretation of line widths of vibrational Stark probes.

Nitrile Vibrational Lifetimes as Probes of Local Electric Fields

“…88 Due to the low thermal population of modes above 600 cm −1 at room temperature, collisional IVR rates (eq S18) were vanishingly small for the nitrile-stretching vibration (mode 136) of Rh800, in agreement with previous nitrilestretch IVR analysis. 88 We subsequently calculated the decay IVR rates for all of the 162 2 = 26,244 possible third-order pathways (eq S17). 95−98 To assign the most probable decay pathway, we first screened our IVR pathways by identifying which pathways were most likely to contribute to the overall decay rate.…”

“…Higher-order processes are possible but tend to be less probable due to weaker couplings; 94 furthermore, higher-order treatment has previously been demonstrated to be unnecessary for quantitative accuracy in lifetime calculations. 75,85,88 Thus, we limit our analysis to third order here.…”

N‑Heterocyclic Carbene Based Pt(II) Complexes with d‐p Transition for Highly Performable Green Phosphorescent Electroluminescence

“…This can be attributed to the more coupled free motions endued by iso‐propyl ( i Pr) substituent. [ 51 ] 52 ] ( Table 1 ) The emission properties of Pt(ppbOppy) and Pt(pibOppy), measured at doping with 5% weight (5 wt.%) in poly(methyl methacrylate) (PMMA) film, were compared with renowned Ir(ppy) 3 (Figure 4b,c). Due to the vibrational restriction imposed by dipp moiety, Pt(ppbOppy) displays an emission peak at 512 nm, with a slightly narrower full width at half maximum (FWHM) of 58 nm.…”

Observing Intramolecular Vibrational Energy Redistribution via the Short-Time Fourier Transform

“…In 1982, Smalley wrote “Intramolecular vibrational randomization (IVR) processes, and their rate, and their degree of completeness have traditionally ranked high among the prime intellectual issues of chemical kinetics,” and he gave 222 references . IVR also denotes intramolecular vibrational (energy) redistribution − and intramolecular vibrational relaxation, − and it is also called intermode energy flow, intramolecular energy flow, and intramolecular energy transfer; we treat all of these terms as synonyms. The process of IVR is hard to study in highly excited molecules due to the anharmonic breakdown of the normal mode picture.…”