High-resolution studies of total electron excitation functions near threshold for the statesBΣu+1and

Abstract

Studies have been made of uv and metastable excitation functions for H2 near threshold.Within 2 eV of threshold the total cross sections appear to be dominated by two vibrational series of resonances. In the excitation function of B~Z+"(uv emitting), one series (band "a") is ten times more intense than the other (band "c"), while for c II"excitation (metastable), the two series have approximately equal intensity. The measured energy positions of the resonant peaks agree-well with results obtained by other experimental techniques and with theory. Energy calibration of the metastable excitation function has confirmed that the c II" (v =0) level is metastable, and there was no obvious threshold for a second metastable vibrational level, although the nature of the data does not preclude its existence.

Electron impact excitation of H2: resonance excitation of B1 u (Jj 2,vj 0) and effective excitation function of EF1 g

“…Resonance excitation of the H 2 B 1 + u state near the threshold energy region has been reported in many early experimental investigations (Kuyatt et al 1966, Heideman et al 1966, Weingartshofer et al 1970, Comer and Read 1971, Sanche and Schulz 1972, Elston et al 1974, McGowan et al 1974. Except in the work of McGowan et al (1974), who measured total optical emission intensities between 1410 and 1770 Å as a function of excitation energy, all other studies measured the electron energy loss of the scattered electron.…”

“…Resonance excitation of the low vibrational levels of the B 1 + u state are thought to take place primarily via two temporary H − 2 states which are generally designated by 'a' and 'c' (Weingartshofer et al 1970, Sanche and Schulz 1972, Schulz 1973, Elston et al 1974, McGowan et al 1974. The vibrational frequencies of both 'a' and 'c' series are found to be ∼0.3 eV.…”

“…Since the electron beam energy width is only 0.8-1.0 eV, the breadth of the resonance excitation function peak indicates the presence of multiple resonance excitation channels. Indeed, experimental studies of Kuyatt et al (1966), Heideman et al (1966), Weingartshofer et al (1970), Comer and Read (1971), Sanche and Schulz (1972) and Elston et al (1974) have shown that resonance excitation of the low v j levels of the B 1 + u primarily takes place via two H − 2 states, which are designated as 'a' and 'c' series, respectively. Based on theoretical calculations by Eliezer et al (1967) and angular distribution measurements by Weingartshofer et al (1970), Comer and Read (1971) have assigned a 2 + g symmetry to the 'a' series.…”

“…Resonance excitation of excited electronic states of H 2 typically takes place between 11 and 16 eV via the formation of a negative molecular anion, which subsequently rapidly (0.1-1 fs) autoionizes to an excited electronic state of the neutral species. The electronic resonance excitation of H 2 by electrons has been reported in the experimental work of Kuyatt et al (1966), Weingartshofer et al (1970Weingartshofer et al ( , 1975, Comer and Read (1971), Golden (1971), Sanche and Schulz (1972), Elston et al (1974), McGowan et al (1974), Schowengerdt and Golden (1975), Böse and Linder (1979) and have been extensively reviewed by Schulz (1973), and Hall and Read (1984).…”

Ab InitioCalculations of Vibrationally Resolved Resonances in Electron Collisions withH2, HD, andD2<

“…Over the last thirty years, many experiments have studied these resonance series for e-H 2 [2][3][4][5][6][7][8][9] as well as e-D 2 [2,6,7,9,10] and e-HD [7,9]. The standard model for these anionic Feshbach-type resonances is that the electron is temporarily trapped in a potential associated with a particular excited state of the target.…”