Observation of anisotropic relaxation in biological molecules with subpicosecond temporal resolution

A new pump–probe technique has been developed for investigation of anisotropic relaxation and energy transfer processes in excited states of polyatomic molecules excited by femtosecond laser pulses. The proposed method was applied for studying the rotational diffusion of NADH with a temporal resolution of about 0.6 ps. Linear dichroism in excited states of biological molecules induced by laser pulses with energy below 1 nJ has been detected for the first time.