Medium-resolution studies of extreme-ultraviolet emission from CO by electron impact.

Abstract

We report medium-resolution [0.025 nm full width at half maximum (FWHM)] electron-impact-induced emission spectra of CO for 20-, 100-, and 200-eV impact energies. The emission spectra correspond to the extreme-ultraviolet transitions from the B $^{1}\mathrm{\ensuremath{\Sigma}}^{+}$(0), $^{1}\mathrm{\ensuremath{\Sigma}}^{+}$(0), and E $^{1}\mathrm{\ensuremath{\Pi}}$(0) vibronic states to the X $^{1}\mathrm{\ensuremath{\Sigma}}^{+}$(0) ground state. The present measurements are carried out at 20 times higher spectral resolution (to separate the many blended components) compared to our previous measurements, which were at a spectral resolution of 0.5 nm FWHM. The emission cross sections corresponding to the B $^{1}\mathrm{\ensuremath{\Sigma}}^{+}$(0) \ensuremath{\rightarrow}X $^{1}\mathrm{\ensuremath{\Sigma}}^{+}$(0), C $^{1}\mathrm{\ensuremath{\Sigma}}^{+}$(0)\ensuremath{\rightarrow}X $^{1}\mathrm{\ensuremath{\Sigma}}^{+}$(0), and E $^{1}\mathrm{\ensuremath{\Pi}}$(0)\ensuremath{\rightarrow}X $^{1}\mathrm{\ensuremath{\Sigma}}^{+}$(0) resonance transitions were measured. In addition, excitation functions (0--1 keV) extending well into the Born region have been measured for the strong transitions [B $^{1}\mathrm{\ensuremath{\Sigma}}^{+}$(0)\ensuremath{\rightarrow}X $^{1}\mathrm{\ensuremath{\Sigma}}^{+}$(0) and $^{1}\mathrm{\ensuremath{\Sigma}}^{+}$(0)\ensuremath{\rightarrow}X $^{1}\mathrm{\ensuremath{\Sigma}}^{+}$(0)] and oscillator strengths have been determined, using a modified-Born-approximation analytic fit to the measured excitation function.