Probing the alignment of NO(X 2Π) by [2+1] resonance-enhanced multiphoton ionization via the C 2Π state: A test of semiclassical theory in 355 nm photodissociation of NO2

Abstract

A theoretical method to analyze the two- and three-dimensional imaging data of photofragments with polarized angular momentum was tested by comparing with the experimental data on NO from 355 nm photodissociation of NO2. The alignment of NO(X 2Π) was detected by [2+1] resonance-enhanced multiphoton ionization via the C 2Π state. The data were analyzed by assuming the μ–ν–J triple vector correlation described by semiclassical multipole moments in the velocity-fixed frame. The geometrical factors for the two-photon absorption were derived rigorously for the intermediate coupling between Hund’s cases (a) and (b). It was also shown, however, that the geometrical factors for high J are independent of the coupling case and can be approximated by simple formulas. Excellent agreement between the simulation and the experimental data proved the validity of the semiclassical treatment.

Some remarks on the photodynamics of NO2

“…65,67,68,74 The fragment rotational distributions tend to unimodal profiles which peak with moderate degrees of fragment rotational excitation as the excess energy in the (1) 2 B 2 state is increased. The photoproduct internal state distributions have been measured right across the first electronic absorption feature in a variety of experiments 46,[74][75][76][77][78][79][80][81][82][83][84][85][86][87][88][89][90][91][92][93] which with the observation of interference or stepwise changes in dissociation timescale with excitation energy 59,60,62,94,95 provide support for the dissociation mechanism outlined above.…”

Imaging Atomic Orbital Polarization in Photodissociation

“…The angular distribution of atomic photofragment alignment resulting from linearly polarized dissociation light has been the subject of dozens of publications since the mid-1990s (see, e.g., refs – ,,,, and – ). However, only a few results have been reported so far on determination of the high rank K = 4 fragment state multipoles. ,,, The anisotropy parameters of the rank K ranging from K = 0 to 2 j A represent a total set of quantum mechanical variables that can be determined from photodissociation of randomly oriented parent molecules and contains all information about the dissociation dynamics.…”

Universal and State-Resolved Imaging of Chemical Dynamics

“…Alternative approaches have long been sought to circumvent these problems and to measure the quantity of interest − the velocity distribution − directly. One such strategy has been the development of data analysis techniques to extract the full velocity and angular information directly from the raw 2D projection images, − and forward convolution methods of this type have enjoyed a considerable degree of success. ,− More recently, efforts to stretch the ion cloud along the flight direction then slice the central section of the fragment distribution have proven very successful, and these have displaced virtually all other approaches in our own laboratory. This idea can be traced to early efforts by Tonokura and Suzuki using “laser sheet” ionization, and more recently efforts by Kitsopoulos and co-workers .…”