THE LOCAL MODE MODEL AND RECENT ADVANCES IN LASER-BASED PHOTOACOUSTIC-SPECTROSCOPY - 1992 GERHARD HERZBERG AWARD ADDRESS

A brief history is given of the development of the local mode model an d a summary of the key features of the model is presented, The model i s used to describe XH stretching overtone spectra. These spectra are v ery weak and are often observed by laser based photoacoustic spectrosc opy. Vapor phase spectra of local mode high energy vibrational overton es are presented as illustrations of the sensitivity of this technique . Recent improvements in the basic experiment are described which invo lve signal averaging, frequency calibration, laser power normalization and other effects. The extensions to lower energies through the use o f a Titanium:Sapphire laser, and to higher energies with the use of '' blue'' dyes are also described.