Vibronic structure and predissociation dynamics of 2-methoxythiophenol (S): The effect of intramolecular hydrogen bonding on nonadiabatic dynamics.

Vibronic spectroscopy and the S-H bond predissociation dynamics of 2-methoxythiophenol (2-MTP) in the S (ππ) state have been investigated for the first time. Resonant two-photon ionization and slow-electron velocity map imaging (SEVI) spectroscopies have revealed that the S-S transition of 2-MTP is accompanied with the planar to the pseudoplanar structural change along the out-of-plane ring distortion and the tilt of the methoxy moiety. The S vibronic bands up to their internal energy of ∼1000 cm are assigned from the SEVI spectra taken via various S vibronic intermediate states with the aid of ab initio calculations.

Experimental observation of nonadiabatic bifurcation dynamics at resonances in the continuum.

The surface crossing of bound and unbound electronic states in multidimensional space often gives rise to resonances in the continuum. This situation happens in the πσ*-mediated photodissociation reaction of 2-fluorothioanisole; optically-bright bound S (ππ*) vibrational states of 2-fluorothioanisole are strongly coupled to the optically-dark S (πσ*) state, which is repulsive along the S-CH elongation coordinate. It is revealed here that the reactive flux prepared at such resonances in the continuum bifurcates into two distinct reaction pathways with totally different dynamics in terms of energy disposal and nonadiabatic transition probability.

Photodissociation Dynamics of Ortho-Substituted Thiophenols at 243 nm.

The photoinduced S-H (D) bond fission dynamics of four ortho-substituted thiophenols, 2-fluoro, 2-chloro, 2-bromo, and 2-methoxythiophenol at a pump wavelength of 243 nm, have been investigated by velocity-map imaging and high-level electronic structure calculations. The D atom images of the deuterated ortho-substituted thiophenols show much reduced X̃/Ã branching ratios of the cofragment radicals over that of bare thiophenol. The angular distributions of the D fragment display negative anisotropies, indicating that transition dipole moments are perpendicular to the fast dissociating S-D bond axis.

Spatial Isolation of Conformational Isomers of Hydroquinone and Its Water Cluster Using the Stark Deflector.

Conformational isomers of hydroquinone and their 1:1 clusters with water have been spatially separated using a Stark deflector in a supersonic jet. trans-Hydroquinone (HyQ) conformer with zero dipole moment is little influenced by inhomogeneous electric fields, whereas cis conformer with nonzero dipole moment (2.38 D) is significantly deflected from the molecular beam axis into the direction along which the strong field gradient is applied.

Dynamic role of the intramolecular hydrogen bonding in nonadiabatic chemistry revealed in the UV photodissociation reactions of 2-fluorothiophenol and 2-chlorothiophenol.

The dynamic interplay between the intramolecular hydrogen bonding and intramolecular vibrational redistribution is found to be critical in nonadiabatic reaction dynamics. Herein, it has been demonstrated that the molecular planarity, directed by the intramolecular hydrogen bonding, plays an important role in the nonadiabatic passage of the reactive flux at the conical intersection in the photodissociation reactions of 2-fluorothiophenol and 2-chlorothiophenol. As the internal energy increases in the excited state, the intramolecular hydrogen bonding of 2-fluorothiophenol loosens.