We present a novel procedure for vibrationally resolved sum-frequency generation (SFG) in which a broad-bandwidth IR pulse is mixed with a narrow-bandwidth visible pulse. The resultant SFG spectrum is dispersed with a spectrograph and detected in parallel with a scientific-grade CCD detector, permitting rapid and high signal-to-noise ratio data acquisition over a 400-cm(-1) spectral region without scanning the IR frequency. Application to the study of a self-assembled monolayer of octadecanethiol is discussed.

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Surface second-harmonic generation (SHG) is recognized as a second-order non-linear laser-based spectroscopy offering good surface sensitivity and selectivity. With the goal of developing optical methods to study chiral surfaces, a way to detect dichroic behaviour in SHG in analogy to circular dichroism (CD) spectroscopy has been elucidated. The SHG efficiency from a monolayer of oriented chiral molecules [(R)or (S)-2,2'-dihydroxy-1,l'-binaphthyl (BN)] has a strong dependence upon whether the excitation beam has left-or right-handed circular polarization. The relative differential SHG signal is much larger than in ordinary CD spectroscopy.The large chiroptical effects in SHG are attributed not to R, the rotational strength responsible for traditional C D (R = Im p * m), but to the electric dipole-allowed second-order non-linear tensor, f 2 ) . There is a chiral element of x('), ;cxyz, that must be included in descriptions of the SHG