Proposed picosecond excited-state measurement method using a tunable-laser-induced grating

This letter analyzes a suggested technique for studying excited atomic or molecular states on a picosecond to subpicosecond time scale by using tunable laser beams, without requiring ultrafast laser pulses or optical detectors. In the proposed technique the frequency transform of the impulse response of an excited state is determined by measuring the diffraction of a cw probe laser beam from a moving excited-state grating induced by two intersecting tunable excitation beams, as the frequency difference between the two cw excitation beams is varied.