Advantage has been taken of the rapid and homogeneous heating of a sample in a shock wave to record the electronic absorption spectra of the 'Al, + lBzu transition in benzene and the corresponding 'Al + 'B1 transition in toluene as a function of temperature over the range 700-1300 K, prior to thermal decomposition.A model for the band-shape function of electronic absorption spectra of symmetry-allowed and symmetry-forbidden transitions in the context of the Herzberg-Teller theory is proposed based upon the assumption of harmonic oscillators. For symmetry-forbidden transitions, frequency changes in the promoting modes are ignored and only the linear Herzberg-Teller terms are considered to account for the dependence of the electronic transition moment upon nuclear coordinates. Explicit attention is paid to the temperature dependence of the band-shape function and it is shown, in conjunction with a moment analysis of the band-shape function, how important molecular parameters may be deduced in favourable instances, which are determined chiefly by the inherent molecular complexity and symmetry point group of the molecule. It is shown by a moment analysis of the shock data that the induced and allowed transition moments in toluene are of comparable magnitude.

This paper presents a theoretical analysis, based on a simplified one-dimensional model, of the response of an explosive to a wide range of light intensities. A primary result has been the identification and development of a relationship among the important critical parameters. Numerical results illustrating the relationship among the critical light intensity, sample dimension, and ambient temperature have been obtained, with lead azide as the example.constant, and V2 the Laplacian operator. In the theory of thermal explosion it is postulated that the critical condition for inflammability is reached when the amount of heat developed by the chemical reaction is just equal to the amount lost to the surroundings. In other words, the conditions under which a stationary state is not possible will then give the critical conditions for explosion (1,4). We then have

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