Robert N. Rosenfeld

Energy disposal in the photofragmentation of W(CO)6: Experimental observations and physical models

Energy disposal to the CO product formed upon the 351 nm photodissociation of W(CO)6 has been monitored using the method of time‐resolved infrared laser absorption spectroscopy. The nascent CO product can be characterized by effective vibrational, rotational, and translational temperatures; Tv=1080±60 K, T0r(v=0)=560±50 K, and T0t(v=0 J=10) =1550±200 K. These results are considered in light of various models for energy disposal in the photofragmentation reaction. Vibrational energy disposal is consistent with a modified version of phase space theory termed ‘‘early’’ phase space theory, EPST. Rotational and translational energy release is not consistent with phase space theory or its variants, e.g., EPST and the separate statistical ensembles model, but appears in qualitative accord with an impulsive model. We propose that, in general, vibrational energy release occurs early in the exit channel for the reaction, relative to rotational and translational energy release.

Photodissociation dynamics of carbon suboxide at 193 and 248 nm

The nascent CO vibrational, rotational, and translational energies, following the UV photolysis of carbon suboxide at 193 and 248 nm, were determined by time‐resolved tunable diode laser infrared absorption spectroscopy. A statistical model for energy disposal fits the experimentally observed vibrational distributions and average translational energies at both photolysis wavelengths. The model fails to account for the experimental rotational distributions that are much ‘‘colder’’ than the model predictions. An impulsive model for dissociation could not account for the observed energy partitioning at both photolysis wavelengths. These results suggest that at 193 nm the primary photoproducts are CO(X1Σ+) and C2O(a1Δ), and that at 248 nm the primary photoproducts are CO(X1Σ+) and C2O(X3Σ−).

A time-resolved tunable diode laser study of the photodissociation dynamics of W(CO)6

Abstract Time-resolved diode laser absorption spectroscopy has been used to study the photodissociation of W (CO) 6 following excitation at 351 nm. The narrow linewidth (≈ 10 −4 cm −1 ) and tunability of this infrared source allows the nascent rotation-vibrational energy distribution of the CO product to be determined. Additionally, translational energy disposal can be characterized by measurements of the shapes of individual rotation-vibration lines. Our results indicate that energy is partitioned preferentially to product translational and vibrational, rather than rotational, motion for the 351 nm photofragmentation of W(CO) 6 .

The photofragmentation dynamics of 3-cyclopentenone in the gas phase

Abstract Vibrational energy disposal to the CO product of the photofragmentation of 3-cyclopentenone has been studied by time-resolved CO laser absorption spectroscopy. The nascent vibrational distribution of CO is N 0 = 7.88, N 1 = 0.187, N 2 = 0.024. The measured vibrational distribution is substantially colder than that predicted on statistical grounds. This indicates that the product fragments become vibrationally decoupled from one another before the full reaction exoergicity has been released. Our results suggest that such decoupling may occur at the dissociation transition state.