Exploring vibrational ladder climbing in vibronic coupling models: Toward experimental observation of a geometric phase signature of a conical intersection

TL;DR

This paper explores how ultrafast IR laser pulses can be used to detect conical intersections in molecules by revealing geometric phase features, advancing spectroscopic methods for identifying these critical points.

Contribution

It introduces optimized multi-pulse laser sequences to stimulate nuclear dynamics for unambiguous detection of conical intersections using nonlinear spectroscopy.

Findings

Optimal laser pulse sequences for CI stimulation identified

Insights into designing spectroscopic schemes for CI detection

Proposals for using ultrafast electron diffraction to observe CIs

Abstract

Conical intersections (CIs) have been widely studied using spectroscopic techniques. However, CIs have mainly been identified by rapid internal conversion transitions that take place after the photoexcitation. Such identifications cannot distinguish various types of intersections as well as to separate the actual intersection from an avoided crossing. In this paper, we investigate how ultrafast IR laser pulses can be utilized to stimulate nuclear dynamics revealing geometric phase features associated with CIs. We consider two low-dimensional nonadiabatic models to obtain optimal two- and three-pulse laser sequences for stimulating nuclear dynamics necessary for the CI identification. Our results provide insights on designing non-linear spectroscopic schemes for subsequent probes of the nuclear wavepackets by ultrafast electron diffraction techniques to unambiguously detect CIs in molecules.