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Electron-impact excitation of the x Σ g − 1 , y<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" …

1990; American Physical Society; Volume: 41; Issue: 3 Linguagem: Inglês

10.1103/physreva.41.1324

1538-4446

James S. Allen, Sunggi Chung, Chun C. Lin,

Cold Atom Physics and Bose-Einstein Condensates

Electron-impact excitation of the x $^{1}\ensuremath{\Sigma}_{g}^{\mathrm{\ensuremath{-}}}$, y $^{1}\ensuremath{\Pi}_{g}$, and ${o}_{3}$ $^{1}\ensuremath{\Pi}_{u}$ Rydberg electronic states of the nitrogen molecule has been studied. We have measured the maximum electron-impact optical-emission cross sections of many vibrational bands of the y $^{1}\ensuremath{\Pi}_{g}$\ensuremath{\rightarrow}w $^{1}\ensuremath{\Delta}_{u}$, y $^{1}\mathrm{\ensuremath{\Pi}}_{\mathrm{g}}$\ensuremath{\rightarrow}a' $^{1}\mathrm{\ensuremath{\Sigma}}_{\mathrm{u}}^{\mathrm{\ensuremath{-}}}$, and x $^{1}\mathrm{\ensuremath{\Sigma}}_{\mathrm{g}}^{\mathrm{\ensuremath{-}}}$\ensuremath{\rightarrow}a' $^{1}\mathrm{\ensuremath{\Sigma}}_{\mathrm{u}}^{\mathrm{\ensuremath{-}}}$ electronic transitions. The maximum values of the optical-emission cross sections of these band systems are typically less than or on the order of ${10}^{\mathrm{\ensuremath{-}}20}$ ${\mathrm{cm}}^{2}$. The dependence of the emission cross sections of selected bands on electron energy has been studied. The excitation functions of the y\ensuremath{\rightarrow}a' and x\ensuremath{\rightarrow}a' bands have similar shapes below about 50 eV with a peak near 32 eV, and are approximately proportional to 1/E at high energies. We have measured the emission cross section of the ${o}_{3}$ $^{1}\ensuremath{\Pi}_{u}$\ensuremath{\rightarrow}a $^{1}\mathrm{\ensuremath{\Pi}}_{\mathrm{g}}$(0,0) band as a function of electron energy. The excitation function of the ${o}_{3}$\ensuremath{\rightarrow}a(0,0) band has a broader shape than the excitation functions of the y\ensuremath{\rightarrow}w, y\ensuremath{\rightarrow}a', and x\ensuremath{\rightarrow}a' bands. We have calculated Franck-Condon factors for the y\ensuremath{\rightarrow}w, y\ensuremath{\rightarrow}a', and x\ensuremath{\rightarrow}a' band systems and compare them with the experimental emission cross sections of these band systems. The apparent electron-impact-excitation cross sections of the vibrational levels of the x and y electronic states are estimated.