DUAL-BEAM SUBPICOSECOND BROAD-BAND INFRARED SPECTROMETER

A method for obtaining broadband multichannel IR spectra with subpicos econd time resolution is described. Spectrally broad IR pulses, produc ed by difference-frequency mixing of two visible pulses in LiIO3, are split to make signal and reference pulses. After sample absorption, th e IR pulses are upconverted by a second LiIO3 crystal to produce visib le pulses that are dispersed on a CCD detector to yield transient spec tra with 100-cm(-1) bandwidth and 4-cm(-1) resolution. With this dual- beam technique, spectra with sensitivities of 0.001 Delta OD are obtai ned.