Imaging studies of excited and dissociative States of hydroxymethylene produced in the photodissociation of the hydroxymethyl radical.

Rotational, vibrational, and electronic states of formaldehyde and cis-hydroxymethylene products generated in the photodissociation of the hydroxymethyl radical are investigated by sliced velocity map imaging (SVMI) following excitation of the radical to its 3px and 3pz Rydberg states. SVMI of H and D photofragments is essential in these studies because it allows zooming in on low-velocity regions of the images where small threshold signals can be identified. With CH2OD precursors, formaldehyde and hydroxymethylene products are examined separately by monitoring D and H, respectively.

Accessing multiple conical intersections in the 3s and 3p(x) photodissociation of the hydroxymethyl radical.

The photodissociation dynamics of the hydroxymethyl radical (CH2OH, CH2OD, and CD2OD) following excitation to the 3s and 3p(x) Rydberg states is studied using time-sliced velocity map imaging of hydrogen photofragments. Dissociation takes place on the ground potential energy surface reached via conical intersections from the excited states, and formaldehyde and hydrxymethylene are identified as reaction products. The major product, formaldehyde, has a bimodal internal energy distribution.

Rotationally resolved C2 symmetric conformers of bis-(4-hydroxyphenyl)methane: prototypical examples of excitonic coupling in the S1 and S2 electronic states.

Rotationally resolved microwave and ultraviolet spectra of jet-cooled bis-(4-hydroxyphenyl)methane (b4HPM) have been obtained using Fourier-transform microwave and UV laser/molecular beam spectrometers. A recent vibronic level study of b4HPM [Rodrigo, C. P.

Conformer-specific vibronic spectroscopy and vibronic coupling in a flexible bichromophore: bis-(4-hydroxyphenyl)methane.

The vibronic spectroscopy of jet-cooled bis-(4-hydroxyphenyl)methane has been explored using fluorescence excitation, dispersed fluorescence (DFL), UV-UV hole-burning, UV depletion, and fluorescence-dip infrared spectroscopies. Calculations predict the presence of three nearly isoenergetic conformers that differ in the orientations of the two OH groups in the para positions on the two aromatic rings (labeled uu, dd, and ud). In practice, two conformers (labeled A and B) are observed, with S(0)-S(1) origins at 35,184 and 35,209 cm(-1), respectively.

Single-conformation ultraviolet and infrared spectra of jet-cooled monolignols: p-coumaryl alcohol, coniferyl alcohol, and sinapyl alcohol.

Single-conformation spectroscopy of the three lignin monomers (hereafter "monolignols") p-coumaryl alcohol (pCoumA), coniferyl alcohol (ConA), and sinapyl alcohol (SinA) has been carried out on the isolated molecules cooled in a supersonic expansion. Laser-induced fluorescence excitation, dispersed fluorescence, resonant two-photon ionization, UV-UV hole-burning, and resonant ion-dip infrared spectroscopy were carried out as needed to obtain firm assignments for the observed conformers of the three molecules. In each case, two conformers were observed, differing in the relative orientations of the vinyl and OH substituents para to one another on the phenyl ring.

Duschinsky mixing between four non-totally symmetric normal coordinates in the S(1)-S(0) vibronic structure of (E)-phenylvinylacetylene: a quantitative analysis.

(E)-Phenylvinylacetylene was shown previously (C.-P. Liu, J.