Ultrasensitive transient time-resolved monitoring of anisotropic relaxation in NADH with sub-picosecond resolution

Abstract

A novel ultrasensitive transient time-resolved monitoring method has been developed suitable for studying of fast anisotropic relaxation in electronic excited states of polyatomic and biologically relevant molecules under excitation with femtosecond laser pulses. The method is based on the modulation of a pump beam polarization with a photo-elastic modulator and highly sensitive balanced detection of mutually orthogonal polarization components of a probe beam with following recording of the differential transient signal with a lock-in amplifier. The method was used for the study of anisotropic relaxation in the first electronic excited state of coenzyme NADH in solutions with various viscosity and polarity.