Measurements of electron attachment lineshapes and cross sections at ultra-low electron energies for CF2Cl2, c-C4F6, c-C4F8and c-C7F14

Electron attachment cross sections are reported in the electron energy range 0-160 meV, and at energy resolutions of 7.0 and 7.5 meV (FWHM), for the molecules CF 2 Cl 2 (dichlorodifluoromethane), c-C 4 F 6 (perfluorocyclobutene), c-C 4 F 8 (perfluorocyclobutane) and c-C 7 F 14 (perfluoromethylcyclohexane). Use is made of the Kr photoionisation method. Measured attachment lineshapes are deconvoluted from the spectral slit function, and are converted to cross sections by normalisation through thermal attachment rate constants. Comparisons are made with attachment cross sections derived from several independent sets of swarm-measured rate constants, and with collisional ionisation (high-Rydberg attachment) data.