Electron collisions with nitrogen trifluoride(NF3)molecules

Abstract

Absolute total cross sections (TCS's) for $0.5--370\text{\ensuremath{-}}\mathrm{eV}$ electrons scattered by nitrogen trifluoride $({\mathrm{NF}}_{3})$ molecules have been measured using a linear transmission method under single collision conditions. It was found that the TCS energy function for ${\mathrm{NF}}_{3}$ is dominated with two pronounced enhancements: one resonantlike centered between 2 and $3\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$ with the maximum value of $28\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}20}\phantom{\rule{0.3em}{0ex}}{\mathrm{m}}^{2}$ followed with a minimum at around $7--12\phantom{\rule{0.3em}{0ex}}\mathrm{eV}(\ensuremath{\sim}17\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}20}\phantom{\rule{0.3em}{0ex}}{\mathrm{m}}^{2})$, and the second much broader enhancement located around $40\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$ ($19\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}20}\phantom{\rule{0.3em}{0ex}}{\mathrm{m}}^{2}$ in the maximum). The low-energy enhancement is superimposed with some weak features located near 1.8, 2.2, and $2.8\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$. The integral elastic cross section has been calculated at intermediate energies using an independent atom method with a static plus polarization model potential. The cross section for ionization has been computed as well using the binary-encounter-Bethe approach. The sum of calculated cross sections reasonably reproduces the intermediate-energy experimental TCS, with respect to the shape and value. The TCS for ${\mathrm{NF}}_{3}$ is also compared with the TCS for ammonia $({\mathrm{NH}}_{3})$ which was supplementary measured and the effect of substitution of fluorine atoms for hydrogen (perfluorination effect) is demonstrated and discussed.