화학공학소재연구정보센터
Journal of Chemical Physics, Vol.111, No.17, 7844-7856, 1999
Dynamics of linear and T-shaped Ar-I-2 dissociation upon B <- X optical excitation: A dispersed fluorescence study of the linear isomer
We report the dispersed fluorescence spectra of the linear and the previously well-studied T-shaped isomers of Ar-I-2 following B <-- X optical excitation for v(pump)=16-26, below the I-2 dissociation limit. The linear isomer has a continuum excitation spectrum. For excitation at the highest pumping energy (v(pump)=26), the product vibrational state distribution is nearly identical to that observed for excitation above the I-2(B) dissociation limit; it shows a broad, nearly Gaussian distribution of I-2(B) vibrational states, with about 22% of the available excess energy deposited in translation of the Ar+I-2. This gives direct evidence that the "one-atom cage" effect seen above the I-2(B) dissociation limit is attributable to the linear Ar-I-2 isomer. The product vibrational state distribution becomes increasingly Poisson for decreasing excitation energies, and only about 7% of the excess energy is deposited in translation for v(pump)=16. The bond energy in the linear isomer is determined from the spectra, 170(+/- 1.5)less than or equal to D-0"(linear Ar-I-2(X))less than or equal to 174(+/- 1.5) cm(-1). A bond energy of D-0"(T-shaped Ar-I-2(X))=142 +/- 15 cm(-1) is estimated based on the linear to T-shaped population ratio observed in the beam, which is about 90 cm(-1) smaller than that determined from fluorescence spectra. We suggest that electronic quenching in the T-shaped isomer is nearly 100% for the highest vibrational level produced by vibrational predissociation.