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Dissociative excitation of methanol (CH3OH) by electron impact leading to the production of O(1S) and CO(a3Π) has been studied in the energy range from threshold to 100 eV using a unique detector which is selectively sensitive to low energy metastable particles. Time of flight (TOF) techniques are used to separate atomic and molecular fragment species. Energy considerations have allowed certain excitation channels producing O(1S) to be identified.

A new magneto-optical trap designed specifically for the measurement of absolute electron impact cross sections is described. Experimental results for electron impact total cross sections involving 6 2 S ground state Cs are presented over the energy range 5–200 eV. Significant disagreement is obtained between our experimental data and convergent close coupling (CCC) or Breit–Pauli R-matrix calculations at the lower energies. Above 100 eV our data overlap earlier measurements from this laboratory made with a completely different apparatus and agree well with the CCC results. A comparison is made with other measurements using more conventional techniques.

Using a time-of-flight technique, we have studied the production of neutral metastable fragments in collisions of electrons with neutral xenon clusters. The data reveal that at least six different processes are occurring, yielding fragments with most probable kinetic energies between 0.08 and 1.6 eV. Additional processes give rise to excited fragments that decay by vacuum ultraviolet photon emission, with a variety of lifetimes. Some excitation routes involve exciton excitation, followed by localization into a dimer state, and subsequent decay into the metastable atomic channel. Others involve localization into a bound dimer state, followed by infrared photon decay to a repulsive curve, with consequent production of energetic metastable fragments.

A novel xenon matrix surface detector is used to study the production of S(1S) atoms following controlled electron impact on CS2 over an energy range from threshold to 400 eV. A crossed-beam apparatus with a pulsed electron beam is used to obtain the time-of-flight, and hence energy spectra of S fragments. The absolute cross section for production of S(1S) reaches a maximum of 3.8 × 10−18 cm2 at an impact energy of 35 eV. The dissociation mechanism proposed by Kistopoulos et al (Kistopoulos T, Gebhardt C R and Rakitzis T P 2001 J. Chem. Phys. 115 9727) is confirmed.

A special matrix isolation detector, sensitive to S(1S0), has been used to study the dissociation of OCS into this fragment over an electron energy range from threshold to 400 eV. The maximum cross section occurs at an impact energy of 55 eV and has been measured to be 3.3×10-17 cm2. Time of flight spectroscopy has been used to monitor fragment kinetic energies. Optically allowed processes are observed to dominate the dissociation. Striking similarities between electron and 157 nm photon dissociation have been noted.

The polarization of Balmer-α radiation excited in collisions of electrons with atomic hydrogen is presented for an electron energy range from threshold to 1000 eV. Measurements are in good agreement with calculations carried out using either convergent-close-coupling or R-matrix with pseudo-states approaches. Cascade is demonstrated to have a significant effect. Balmer-α excitation function data are also presented. A previous measurement of the polarization of Balmer-α following dissociative excitation of H2 by electrons is confirmed and extended.

The interaction of electrons of carefully controlled energy with N2O molecules and clusters has been studied in a pulsed crossed-beam arrangement over the energy range from threshold to 200 eV. A variety of time-resolved techniques have been applied to isolate and study many of the dissociative excitation channels which occur. The data obtained are relatively insensitive to the degree of clustering in the target beam.

Total fragmentation of and has been studied as a function of incident energy over the range from threshold to 325 eV. A small subset of possible dissociation channels has been selected by making use of a novel solid xenon matrix detector which is selectively sensitive to metastable atoms. O-fragment kinetic energies and appearance potentials have been measured and significant isotopic effects are observed. Within the errors of the measurements the cross section for production from is the same as that from . The cross sections reach a maximum value of at 100 eV incident electron energy.