A molecular beam of halothane (2-bromo-2-chloro-1,1,1-trifluoroethane) is focused by a hexapolar electrostatic field and photolyzed by UV laser radiation at 234 nm. Angular and speed distributions of chlorine and bromine photofragments emitted from halothane are measured for both spin–orbit states independently. Although the dissociation energy of the C–Cl bond is larger than that of C–Br, the relative yield of Cl to Br was found to be approximately 2. Measured speed and angular distributions of atomic fragments show distinct kinetic energy release and scattering characteristics: for bromine, observed fast and aligned fragments exhibit a signature of a direct mode of dissociation for the C–Br bond, via the electronically excited potential energy surface denoted nσ*­(C–Br), of repulsive nature; for chlorine, a variation in the features is observed for the dissociation pathway through nσ*­(C–Cl), from a modality similar to the bromine case, leading to fragments with appreciable kinetic energy release and pronounced directionality, to a modality involving slow products, nearly isotopically distributed. The origin of this behavior can be attributed to nonadiabatic interaction operating between the nσ*­(C–Br) and nσ*­(C–Cl) surfaces. These results are not only relevant for a detailed understanding of adiabatic versus diabatic coupling mechanisms in the manifold of excited states populated by photon absorption, but they also point out the possibility of selectively inducing specific dissociation pathways, even when involving energetically unfavorable outcomes, such as, in this case, the prevailing rupture of the stronger C–Cl bond against that of the weaker C–Br bond.

Both single-laser and two-laser experiments were conducted to look into the ion-imaging of Br*( 2 P1/2) and Br( 2 P3/2) photo-fragmented from 1-bromo-2-methylbutane in the range 232-240 nm via a detection scheme of (2+1) resonance-enhanced multiphoton ionization. The angular analysis of these photofragment distributions yields the anisotropy parameter β = 1.88 ± 0.06 for the Br* excited state which arises from a parallel transition, while β = 0.63 ± 0.09 for the Br ground state indicates the contribution from both a perpendicular transition and a non-adiabatic transition. When a hexapole coupled with an orienting field was implemented, the parent molecules are spatially oriented to yield an orientation efficiency || of 0.15. Besides the χ angle between the recoil velocity v and the transition dipole moment μ, orienting molecules allows for the evaluation of the angle α between v and the permanent molecular dipole moment d. The angular analysis of Br * photofragment distribution yields χ to be 11.5° and α in the range from 160° to 180° with weak dependency. In the two-laser experiments, the angular anisotropy of Br photofragment distribution was found to be smaller (0.38 ± 0.10) when the photolysis wavelength was red-shifted to 240 nm, suggesting the increasing contributions from perpendicular transitions.

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Aiming at artwork restoration application, to decolor the blue‐ink stained marble stone surface was studied for finding out efficient ablation conditions with the use of Q‐switched Nd:YAG laser as the function of laser flux power, wavelength, and its water spray effect. The blue ink mostly consists of indigo dye which absorbs light in the visible region. The decoloration, or decolor efficiency, was evaluated by using the grayscale representation instead of the RGB method. Our experimental results show that the 532 and 355 nm wavelengths are more suitable for blue‐ink decoloration. No decoloration was observed at the 1,064 nm ablation, which is usually regarded as effective on black‐crust stained surfaces. The decolor effect of the water‐sprayed surface was found to be effective at the higher laser flux power. A photo‐absorption‐assisted laser ablation mechanism is proposed in addition to the plasma‐assisted laser ablation mechanism.

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