Transient Two-Dimensional Electronic and Time-Resolved Heterodyne-detected Vibrational sum frequency Spectroscopy: Probing Ultrafast Nonequilibrium Dynamics in Molecular and Interfacial Systems

PC Special Seminar
Date: Feb 27, 2026
Time: 11:30 AM (Local Time Germany)
Speaker: Jan-Hendrik Borter
RIKEN, Japan
Location: Building G
Room: 2.06
Host: Alexander Paarmann
Topic: Discussion and debate formats, lectures

Ultrafast spectroscopy provides direct experimental access to a wide range of nonequilibrium dynamics in condensed-phase systems. Advances in laser sources and detection schemes have continuously expanded the range of photophysical processes that can be experimentally addressed. Building on my strong foundation in femtosecond transient absorption spectroscopy (TAS), I recently had the opportunity to learn two new very sophisticated experimental techniques:

Transient two-dimensional electronic spectroscopy (tr-2DES) enabled me to investigate the complex excited-state dynamics of a well-known photochromic molecular switch using two consecutive pump excitations, including its excited-state heterogeneity emerging upon initial excitation.
Using time-resolved heterodyne-detected vibrational sum frequency generation (tr-HD-VSFG) spectroscopy, I measured the transient imaginary χ(2) response following vibrational excitation of the O–H stretch modes at the silica–HOD interface, allowing me to probe the dependence of vibrational relaxation dynamics on pump excitation energy.
In this talk, I will present my most recent research, beginning with a short summary of projects from my core expertise in fs-TAS, before transitioning toward projects involving the more sophisticated tr-2DES and tr-HD-VSFG, and illustrate how these experimental techniques enabled me to probe aspects of ultrafast nonequilibrium dynamics in molecular and interfacial systems.