High resolution slice imaging of nonadiabatic state - to - state photodynamics

  • Published 2008


Absorption of photons by molecules opens various molecular decay channels. The breaking of a molecular bond due to the exposure to light is a common definition of the photodissociation process. The difference between the photon energy and the bond dissociation energy, known as the excess energy, may be distributed among all available degrees of freedom of the nascent fragments (translational and internal). The proportion of the excess energy released as kinetic energy as well as the masses of the nascent photofragments will determine their recoil speed. The residual excess energy is distributed over the other degrees of freedom of the fragments and may lead to rotational, vibrational and electronic excitation of the fragments. Velocity map slice imaging technique is a powerful tool for studying the gas phase molecular reaction dynamics. This technique allows simultaneous measurement of the rotational, vibrational, electronic and translational energy distribution of the products of a unimolecular reaction and it is used in this thesis to investigate the reaction of gas phase molecule with light. The design of an electrostatic ion lens for photodissociation of spatially oriented parent molecules in combination of slice imaging of the angular distribution of photofragments is presented in Chapter 2. With the slice imaging technique the spatial distribution of oriented recoiling photofragments can be measured without symmetry restriction and with high resolution. The orientation electrodes are inserted in between the repeller and the extractor electrodes of the ion lens. The dimensions and position of the orientation electrodes are very important since its presence will distort the electric field within the ion lens and will affect the ions trajectories. The combination of molecular orientation and velocity map slice imaging is experimentally demonstrated on the dissociation of rotationally state-selected and spatially oriented CD3I at 266 nm and the (2+1) REMPI detection of the CD3 photofragments. This orientation ion lens provides slice imaging of photofragments from oriented photodissociation with good quantitative accuracy. In Chapter 3 the experimental design and performance of the large frame centroiding imaging detector for high-resolution velocity map slice imaging of photofragments is described in detail. The detector combines fast gain gating and on-the-fly centroiding of ion events. The intensity distribution of individual light spots is con-

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@inproceedings{2008HighRS, title={High resolution slice imaging of nonadiabatic state - to - state photodynamics}, author={}, year={2008} }