Elastic and inelastic cross sections for low-energy electron collisions with pyrimidine.

We present theoretical elastic and electronic excitation cross sections and experimental electronic excitation cross sections for electron collisions with pyrimidine. We use the R-matrix method to determine elastic integral and differential cross sections and integral inelastic cross sections for energies up to 15 eV. The experimental inelastic cross sections have been determined in the 15-50 eV impact energy range.

A velocity map ion imaging study of difluorobenzene-water complexes: binding energies and recoil distributions.

The binding energies of the p-, m-, and o-difluorobenzene-H(2)O complexes have been measured by velocity map ion imaging to be 922+/-10, 945+/-10, and 891+/-4 cm(-1), respectively. The lack of variation provides circumstantial evidence for water binding to the three isomers via the same interaction, viz. an in-plane O-H.

An unusual pi* shape resonance in the near-threshold photoionization of S1 para-difluorobenzene.

Previously reported dramatic changes in photoelectron angular distributions (PADs) as a function of photoelectron kinetic energy following the ionization of S1 p-difluorobenzene are shown to be explained by a shape resonance in the b(2g) symmetry continuum. The characteristics of this resonance are clearly demonstrated by a theoretical multiple-scattering treatment of the photoionization dynamics. New experimental data are presented which demonstrate an apparent insensitivity of the PADs to both vibrational motion and prepared molecular alignment, however, the calculations suggest that strong alignment effects may nevertheless be recognized in the detail of the comparison with experimental data.

Recoil energy distributions for dissociation of the van der Waals molecule p-difluorobenzene-Ar with 450-3000 cm(-1) excess energy.

Velocity map imaging has been used to measure the distributions of translational energy released in the dissociation of p-difluorobenzene-Ar van der Waals complexes from the 5(1), 3(1), 5(2), 3(1)5(1), 5(3), 3(2), and 3(2)5(1) states. These states span 818-3317 cm(-1) of vibrational energy and correspond to a range of energies above dissociation of 451-2950 cm(-1). The translational energy release (recoil energy) distributions are remarkably similar, peaking at very low energy (10-20 cm(-1)) and decaying in an exponential fashion to approach zero near 300 cm(-1).

Rotational distributions following van der Waals molecule dissociation: comparison between experiment and theory for benzene-Ar.

The translational energy release distribution for dissociation of benzene-Ar has been measured and, in combination with the 6(1)(0) rotational contour of the benzene product observed in emission, used to determine the rotational J,K distribution of 0(0) benzene products formed during dissociation from 6(1). Significant angular momentum is transferred to benzene on dissociation. The 0(0) rotational distribution peaks at J=31 and is skewed to low K:Javerage=27, (K)average=10.

Reevaluation of the use of photoelectron angular distributions as a probe of dynamical processes: strong dependence of such distributions from s1 paradifluorobenzene on photoelectron kinetic energy.

Photoelectron angular distributions (PADs) have been measured following the excitation of the S1 origin band in paradifluorobenzene using a range of ionizing wavelengths and for resolved ion vibrational states. The PADs show a dramatic sensitivity to the photoelectron kinetic energy over an energy range of at least 1 eV from threshold, and almost no sensitivity to any prepared intermediate state alignment. This has important consequences for those studies of intramolecular dynamics that use PADs.