TY - GEN
T1 - Intracavity laser photoelectron spectroscopy of Cr2-, Cr2H-, and Cr2D-
AU - Casey, Sean M.
AU - Leopold, Doreen G.
PY - 1992
Y1 - 1992
N2 - The photoelectron spectrum of Cr2- shows vibrational levels in the 1Σg+ ground state of the neutral molecule up to 7300 cm-1 above its zero point level. These data, obtained at an instrumental resolution of 5 meV (40 cm-1), reveal a panoramic view of the controversial ground state potential curve of Cr2. Low-lying vibrational levels are found to fit a Morse potential with approximately egae = 479 ± 2 cm-1 and approximately egaeχe = 13.5 ± 1.0 cm-1. This unusually large anharmonicity extrapolates to a dissociation asymptote of only 0.5 eV, considerably lower than the true 1.44 eV value. Between 4875 and 7320 cm-1 above the zero point level, we observe twenty peaks at 130 ± 15 cm-1 intervals, which we assign as transitions from the ground electronic and vibrational state of the anion to high vibrational levels of the Cr2 ground state. Using an RKR inversion procedure, we have obtained a potential curve that fits all of the observed vibrational levels to within our experimental uncertainty. This potential curve is compared with the predictions of Goodgame and Goddard's modified GVB calculation. Transitions to highly excited vibrational levels of the Cr2 ground state are far more intense than would be expected for a direct photodetachment process, and are also strongly wavelength dependent. These non-Franck-Condon intensities are attributed to a resonance of the laser with one or more metastable states of the negative ion far above the electron detachment threshold. The electron affinity of Cr2 is measured to be 0.505 ± 0.005 eV. An excited electronic state of Cr2 with a vibrational frequency of 580 ± 20 cm-1 is observed 14,240 ± 30 cm-1 above the ground state. For Cr2-, we obtain approximately egae = 470 ± 25 cm-1, approximately ega eχe = 20 ± 10 cm-1, and re = 1.71 ± 0.01 angstrom. Tentative state assignments of 1Σu+ or 3Σ u+ for the excited Cr2 state, and 2Σu+ for the anion, are discussed. Preliminary results for Cr2H- and Cr2D- are also presented. The photoelectron spectra of these anions reveal the Cr-Cr and Cr-H stretching frequencies in the neutral molecules, and exhibit partially resolved rotational structure.
AB - The photoelectron spectrum of Cr2- shows vibrational levels in the 1Σg+ ground state of the neutral molecule up to 7300 cm-1 above its zero point level. These data, obtained at an instrumental resolution of 5 meV (40 cm-1), reveal a panoramic view of the controversial ground state potential curve of Cr2. Low-lying vibrational levels are found to fit a Morse potential with approximately egae = 479 ± 2 cm-1 and approximately egaeχe = 13.5 ± 1.0 cm-1. This unusually large anharmonicity extrapolates to a dissociation asymptote of only 0.5 eV, considerably lower than the true 1.44 eV value. Between 4875 and 7320 cm-1 above the zero point level, we observe twenty peaks at 130 ± 15 cm-1 intervals, which we assign as transitions from the ground electronic and vibrational state of the anion to high vibrational levels of the Cr2 ground state. Using an RKR inversion procedure, we have obtained a potential curve that fits all of the observed vibrational levels to within our experimental uncertainty. This potential curve is compared with the predictions of Goodgame and Goddard's modified GVB calculation. Transitions to highly excited vibrational levels of the Cr2 ground state are far more intense than would be expected for a direct photodetachment process, and are also strongly wavelength dependent. These non-Franck-Condon intensities are attributed to a resonance of the laser with one or more metastable states of the negative ion far above the electron detachment threshold. The electron affinity of Cr2 is measured to be 0.505 ± 0.005 eV. An excited electronic state of Cr2 with a vibrational frequency of 580 ± 20 cm-1 is observed 14,240 ± 30 cm-1 above the ground state. For Cr2-, we obtain approximately egae = 470 ± 25 cm-1, approximately ega eχe = 20 ± 10 cm-1, and re = 1.71 ± 0.01 angstrom. Tentative state assignments of 1Σu+ or 3Σ u+ for the excited Cr2 state, and 2Σu+ for the anion, are discussed. Preliminary results for Cr2H- and Cr2D- are also presented. The photoelectron spectra of these anions reveal the Cr-Cr and Cr-H stretching frequencies in the neutral molecules, and exhibit partially resolved rotational structure.
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U2 - 10.1117/12.58161
DO - 10.1117/12.58161
M3 - Conference contribution
AN - SCOPUS:0026477483
SN - 0819407844
SN - 9780819407849
T3 - Proceedings of SPIE - The International Society for Optical Engineering
SP - 234
EP - 244
BT - Proceedings of SPIE - The International Society for Optical Engineering
PB - Publ by Int Soc for Optical Engineering
T2 - Optical Methods for Time- and State-Resolved Chemistry
Y2 - 23 January 1992 through 25 January 1992
ER -