N,K Rotational Level Populations of CD3 from the 266 nm Photofragmentation of |JKM) State-Selected CD3I

Abstract

The photofragmentation of IJKM) = 11 11) state-selected CD31 was performed at 266 nm. The INK) rotational energy level distribution of the resulting vibrationless CD3 photofragment was determined using ( 2 + 1) resonance-enhanced multiphoton ionization. The INK) distribution showed that the dominant mechanism during the dynamics on the excited 3Q0 surface was A K = 0 scattering between the initially excited parent CD31 and the CD3 fragment, i.e., no relative orbital motion about the original C3 axis of the parent, in agreement with previous non-state selected experiments. In addition, smaller but significant amounts of A K = f 3 scattering also occurred. The outline of a model is provided which attributes the effect of nonhelicity conservation and the A K = f 3 propensity to scattering from regions near the conical intersection between the 3 Q~ and 'QI surfaces and in particular to the coupling term between these surfaces. It is therefore suggested that the relative population of the CD3 INK) energy levels for a given N might provide a quantitative measure of the strength of the nonadiabatic coupling between the two surfaces that correlate asymptotically to the 2P3/2 and 2 P~/ 2 spin-orbit energy levels of the atomic iodine photofragment. The experimental INK) rotational distributions are also compared to two recent quantum calculations and are found to be in good agreement for the total scattering into all K levels for a given N . Experimental evidence is also provided, although not analyzed, for the first observation of a detailed photofragmentation differential cross section.

Photodissociation of CD3SCD3 on the First Absorption Band: Translational and Internal Energy Transfer to the CD3 Fragment Studied by Resonant Multiphoton Ionization and Time-of-Flight Spectrometry

“…25,[33][34][35] This is confirmed by the analysis of our CD 3 REMPI spectrum of Figure 6 where the simulation performed with the low K propensity distribution F 2 (K|N) (also shown in Figure 6) provides the best overall fit to the experiment.…”

New Laser-Based and Imaging Methods for Studying the Dynamics of Molecular Collisions

“…163, [165][166][167][168] Orientation and alignment can often be verified by photodissociation of the aligned species and examination of the angular distribution of the products. [183][184][185][186][187] Let us examine results from an orientation experiment in which the stereodynamics of the Rb + CH 3 I f CH 3 + RbI reaction were investigated at a rather low collision energy (around 0.1 eV). 165,188 A hexapole focusing field was used to state-select methyl iodide molecules before they passed into a region of linear electric field.…”

Resonance-enhanced multiphoton ionization spectroscopy of CH3 and CD3. Two-photon absorption selection rules and rotational line strengths of the ν3- and ν4-active vibronic transitions

“…Resonance-enhanced multiphoton ionization (RE-MPI) spectroscopy of the methyl radical [1][2][3][4] has been proven to be a powerful technique to study the photodissociation dynamics of its precursors [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20]. To extract information on the population distribution of methyl radicals in various rotational states, the rotationally resolved 0 0 0 vibronic band of the two-photon transition jnp 2 A 00 2 i jX 2 A 00 2 i (n ¼ 3 or 4) in the REMPI spectrum has been thoroughly investigated [2][3][4]8].…”

“…In addition, predissociation-broadened linewidths [2] render the K-resolved REMPI study a difficult task. Consequently, only a deductive procedure could be implemented to obtain the population and alignment parameters of the various jN ; Ki levels of the methyl photofragment [10,12] from the experimental REMPI spectra.…”