F. J. Northrup and Trevor J. Sears, "Stimulated-emission pumping spectroscopy study of jet-cooled C3: pure bending levels and bend–symmetric-stretch combination levels of X˜1Σg+," J. Opt. Soc. Am. B 7, 1924-1934 (1990)
Stimulated-emission pumping spectra were recorded for many pure bending levels [(0, 2, 0)–(0, 34, 0)] and bend–symmetric-stretch combination levels [(1, 0, 0)–(1, 8, 0) and (3, 4, 0)–(3, 8, 0)] in the
state of C3 following excitation of transitions in the
band system. Rotational levels to J = 16 were probed and, because of strong mixing of vibrational angular momentum components, levels with l up to 8 were observed. A rotational analysis was carried out by means of a simple rigid-rotor harmonic-oscillator model for a linear molecule. An adequate fit was obtained, showing that all these vibrational levels could be described by a linear average geometry even though the bending vibration is known to be of extremely large amplitude. Bυ was found to increase strongly with υ2 and to decrease with excitation in ν1. Interpretation of the physical meaning of the resulting parameters is difficult, however, since the vibrational potential is not well described by a harmonic oscillator.
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Only excited levels with Π vibronic symmetry (K = 1) were pumped.
Relative to the J = 0 level of the
ground state of the molecule.
No vibrational assignments were made for these levels.
Table 2
Rotational Energy Levels of the 0, 16, 0 Vibrational Level of C3
Numbers in parentheses are one standard deviation of the fitted parameter.
From the fit of Ref. 5.
From a combination of our SEP data and some higher J data from Ref. 5. Dυ for these levels was fixed at the value determined for 0, 2, 0.
Determined from the frequency difference between the pump and dump lasers.
Relative to the energy, G0(1, 0, 0), which was determined to be 1226.6 cm−1 from the difference of the pump- and dump-laser frequencies.
Relative to the energy, G0(3, 4, 0), which was determined to be 4146.3 cm−1 from the difference of the pump- and dump-laser frequencies.
Tables (3)
Table 1
Ã1Πu Vibronic Level Assignments and Transition Frequencies from
for Pump Transitions for Stimulated-Emission Pumping Spectra
Only excited levels with Π vibronic symmetry (K = 1) were pumped.
Relative to the J = 0 level of the
ground state of the molecule.
No vibrational assignments were made for these levels.
Table 2
Rotational Energy Levels of the 0, 16, 0 Vibrational Level of C3
Numbers in parentheses are one standard deviation of the fitted parameter.
From the fit of Ref. 5.
From a combination of our SEP data and some higher J data from Ref. 5. Dυ for these levels was fixed at the value determined for 0, 2, 0.
Determined from the frequency difference between the pump and dump lasers.
Relative to the energy, G0(1, 0, 0), which was determined to be 1226.6 cm−1 from the difference of the pump- and dump-laser frequencies.
Relative to the energy, G0(3, 4, 0), which was determined to be 4146.3 cm−1 from the difference of the pump- and dump-laser frequencies.