Transient Rydberg Absorption Spectroscopy of Electron Beam Excited Rare Gases

104 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1985.Transient absorption spectra of molecular and atomic Rydberg transitions in the ultraviolet, visible, and near infrared (220 (LESSTHEQ) (lamda) (LESSTHEQ) 900 nm) spectral regions have been observed in electron beam exci- ted rare gases. The most prominent molecular bands for He(,2), Ne(,2),Ar(,2), Kr(,2), and Xe(,2) are assigned to the mp('3)(PI)(,g) (LESSTHEQ) ns('3)(SIGMA)(,u)('+) (He: n = 2, 3 (LESSTHEQ) m (LESSTHEQ) 10; Ne: n = 3, 4 (LESSTHEQ) m (LESSTHEQ) 10; Ar: n = 4, 5 (LESSTHEQ) m (LESSTHEQ) 15; Kr: n = 5, 6 (LESSTHEQ) m (LESSTHEQ) 16; Xe: n = 6, 8 (LESSTHEQ) m (LESSTHEQ) 11) Rydberg series of the dimer. Adiabatic ionization potentials, relative to the respective ns ('3)(SIGMA)(,u)('+) state, are determined by extrapolation of the series to their limits(m (--->) (INFIN)) to be 34361.4 (+OR-) 30 cm('-1) (4.260 (+OR-) 0.004 eV) for He(,2),34396.3 (+OR-) 25 cm('-1) (4.265 (+OR-) 0.003 eV) for Ne(,2), 29351.9 (+OR-) 15 cm('-1) (3.639 (+OR-) 0.002 eV) for Ar(,2), 28428.5 (+OR-) 10 cm('-1) (3.525 (+OR-) 0.001 eV) forKr(,2), and 26664.5 (+OR-) 250 cm('-1) (3.306 (+OR-) 0.031 eV) for Xe(,2). Absorption bands which are ascribed to m'p('3)(SIGMA)(,g)('+) (<---) ns ('3)(SIGMA)(,u)('+) Rydberg series of Ne(,2)(m' = 4,6,8), Ar(,2)(5 (LESSTHEQ) m' (LESSTHEQ) 10) and Kr(,2)(6 (LESSTHEQ) m' (LESSTHEQ) 10) are also reported, and the ionization potentials found to be identical to the respective values quoted above. All of the observed molecular Ryd- berg states have an A('2)(SIGMA)(, 1/2u)('+) ion core. The lowest vibrational quanta ((DELTA)G(, 1/2)) for the ns('3)(SIGMA)(,u)('+) states are determined from vibronic structurein the Rydberg transitions to be 1723 cm('-1) for He(,2), 539 cm('-1) for Ne(,2), 302 cm('-1) for Ar(,2), 172 cm('-1 )for Kr(,2) and 135 cm('-1) for Xe(,2), and are con- sistent with previously reported values. The instability of this statewith respect to the dimer ion core potential D(,0)(A('2)(SIGMA)(, 1/2u)('+))-D(,0)(ns('3)(SIGMA)(,u)('+)) is accurately calculated to be 0.508 (+OR-) 0.004 eV for He(,2), 0.681 (+OR-)0.003 eV for Ne(,2), 0.572 (+OR-) 0.002 eV for Ar(,2), 0.560 eV (+OR-) 0.001 eV for Kr(,2) and 0.52 (+OR-) 0.03 eV for Xe(,2). Using these values and those reported for the dissociation energy of the dimer ion A('2)(SIGMA)(, 1/2u)('+) state, D(,0)(ns('3)(SIGMA)(,u)('+)) is estimated (Ne(,2): 0.67 (+OR-) 0.07 eV; Ar(,2): 0.76 (+OR-) 0.02 eV; Kr(,2): 0.62 (+OR-) 0.02 eV; Xe(,2): 0.52 (+OR-) 0.03 eV). The mp('3)(PI)(,g) Rydberg states are correlated with the plausible atomic asymptotes (mp 3/2 (,2) +('1)S(,0)) by comparison of energy level spacings, quantum defects, and absorption oscillator strengths between the molecular and atomic transitions. Finally, the suppression of gain in e-beam excited visible and UV lasers, by atomic and molecular Rydberg absorptions, is discussed and illustrated for several excimer laser transitions.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD