No abstract

Differential cross section measurements for the elastic scattering of electrons from CH 3 Cl at energies from 0.5 to 9.5 eV are reported for scattering angles of 30° and 100°. The angular scattering dependence is determined at selected energies over this range. At energies below 1.0 eV, the cross sections are in excellent agreement with calculations using the Born dipole approximation. At large angles and higher energies, the scattering is dominated by a 2 A 1 temporary negative ion state near 3.5 eV. Energy loss data at 3.5, 5.0, and 8.5 eV are reported and the relative contributions of various vibrational modes determined. Differential cross sections for vibrational excitation of the 3 a 1 C-Cl and 4 (e) CH stretching modes have been measured. The latter reveals a broad shape resonance of 2 E symmetry peaking near 5.5 eV. Angular distributions for excitation of these same modes are also reported. Using fittings to the vibrational excitation functions, the resonance parameters have been extracted and used in a mixed semiempirical ab initio calculation to compute the relative strengths of the vibrational energy loss peaks. These compare favorably with the results of the experiment. Elastic cross sections integrated over angle are reported for low energies. They are substantially larger than the results from recent measurements of the total cross section.

A.1.11.2 Tertiary particle production by muons interacting in the environment outside the detector . . . A-25 A.1.11.3 Particle production by unseen muons inside the detector .

In a crossed-beam experiment, the authors have studied vibrationally elastic and inelastic scattering of electrons by CF4 in the energy range 0.3-20 eV. The angular range covered by the measurements is from 10' to 105'. In the present paper, they report their results for elastic scattering. Absolute values of the differential cross section (DCS) are determined with reference to the total cross section measured by Jones (1986). For energies above 10 eV, the experimental results are well described by the 'static-exchange' multichannel Schwinger variational principle (SMC) calculations of Huo (1988). At lower energies, the measurements show strong deviations from the calculated results which are attributed to neglect of the polarization effects in the calculations. The elastic e-CF4 scattering shows a Ramsauer-Townsend effect below E=0.5 eV. The data have been evaluated by means of a modified effective range theory (MERT) analysis, and the resulting integral cross sections are compared with results from swarm experiments.

For pt.III see ibid., vol.25, no.7, p.1621-32 (1992). Differential cross sections are presented for vibrationally elastic and inelastic e-CF2Cl2 scattering in the energy range 0.5-10 eV. All four low-lying sigma * valence type resonances are observed in the measurements. The hitherto unidentified B1 (C-F sigma *) resonance has been located at 5.0-5.5 eV. A quite selective excitation of CF2 and CCl2 stretching modes is observed corresponding to the respective valence character of the resonance and in agreement with the symmetry selection rules. Resonance-enhanced vibrational excitation is found to be most pronounced in the totally symmetric resonances of symmetry type A1. The results are discussed in comparison with dissociative attachment experiments. Below 1 eV, similar to the other molecules in this series (CF4, CF3Cl), direct scattering leads to strong excitation of stretching modes according to their IR activity.