title: Linear dichroism amplification: adapting a long-known technique for ultrasensitive femtosecond IR spectroscopy.
abstract: We demonstrate strong amplification of polarization-sensitive transient IR signals using a pseudo-null crossed polarizer technique first proposed by Keston and Lospalluto [Fed. Proc. 10, 207 (1951)] and applied for nanosecond flash photolysis in the visible by Che et al. [Chem. Phys. Lett. 224, 145 (1994)]. We adapted the technique to ultrafast pulsed laser spectroscopy in the infrared using photoelastic modulators, which allow us to measure amplified linear dichroism at kilohertz repetition rates. The method was applied to a photoswitch of the N-alkylated Schiff base family in order to demonstrate its potential of strongly enhancing sensitivity and signal to noise in ultrafast transient IR experiments, to simplify spectra and to determine intramolecular transition dipole orientations.
authors: Physikalisch-Chemisches Institut, Universität Zürich, Winterthurerstrasse 190, 8057 Zürich, Switzerland.
authors: Julien
authors: J
authors: Réhault
authors: Vinicio
authors: V
authors: Zanirato
authors: Massimo
authors: M
authors: Olivucci
authors: Jan
authors: J
authors: Helbing
mesh_terms: D004867:Equipment Design; D012545:Schiff Bases / Q000737:chemistry; D012680:Sensitivity and Specificity; D017550:Spectroscopy, Fourier Transform Infrared / Q000295:instrumentation* / Q000379:methods; D013997:Time Factors
chemical_list: D012545:Schiff Bases