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High-resolution laser spectroscopy of NO2 just above the X(2)A(1)-A(2)B(2) conical intersection
- Source :
- Journal of Chemical Physics, 112(8), 3633-3642. AMER INST PHYSICS
- Publication Year :
- 2000
-
Abstract
- The complexity of the absorption spectrum of NO2NO2 can be attributed to a conical intersection of the potential energy surfaces of the two lowest electronic states, the electronic ground state of 2A12A1 symmetry and the first electronically excited state of 2B22B2 symmetry. In a previous paper we reported on the feasibility of using the hyperfine splittings, specifically the Fermi-contact interaction, to determine the electronic ground state character of the excited vibronic states in the region just above the conical intersection; 10 000 to 14 000 cm−114 000 cm−1 above the electronic ground state. High-resolution spectra of a number of vibronic bands in this region were measured by exciting a supersonically cooled beam of NO2NO2 molecules with a narrow-band Ti:Sapphire ring laser. The energy absorbed by the molecules was detected by the use of a bolometer. In the region of interest, rovibronic interactions play no significant role, with the possible exception of the vibronic band at 12 658 cm−1,12 658 cm−1, so that the fine- and hyperfine structure of each rotational transition could be analyzed by using an effective Hamiltonian. In the previous paper we restricted ourselves to an analysis of transitions of the K⎯=0K−=0 stack. In the present paper we extend the analysis to transitions of the K⎯=1K−=1 stack, from which, in addition to hyperfine coupling constants, values of the AA rotational constants of the excited NO2NO2 molecules can be determined. Those rotational constants also contain information about the electronic composition of the vibronic states, and, moreover, about the geometry of the NO2NO2 molecule in the excited state of interest. The results of our analyses are compared with those obtained by other authors. The conclusion arrived at in our previous paper that determining Fermi-constants is useful to help characterize the vibronic bands, is corroborated. In addition, the AA rotational constants correspond to geometries that are consistent with the electronic composition of the relevant excited states as expected from the Fermi-constants.<br />The complexity of the absorption spectrum of NO2 can be attributed to a conical intersection of the potential energy surfaces of the two lowest electronic states, the electronic ground state of 2A1 symmetry and the first electronically excited state of 2B2 symmetry. In a previous paper we reported on the feasibility of using the hyperfine splittings, specifically the Fermi-contact interaction, to determine the electronic ground state character of the excited vibronic states in the region just above the conical intersection; 10 000 to 14 000 cm−1 above the electronic ground state. High-resolution spectra of a number of vibronic bands in this region were measured by exciting a supersonically cooled beam of NO2 molecules with a narrow-band Ti:Sapphire ring laser. The energy absorbed by the molecules was detected by the use of a bolometer. In the region of interest, rovibronic interactions play no significant role, with the possible exception of the vibronic band at 12 658 cm−1, so that the fine- and hyperfine structure of each rotational transition could be analyzed by using an effective Hamiltonian. In the previous paper we restricted ourselves to an analysis of transitions of the K⎯=0 stack. In the present paper we extend the analysis to transitions of the K⎯=1 stack, from which, in addition to hyperfine coupling constants, values of the A rotational constants of the excited NO2 molecules can be determined. Those rotational constants also contain information about the electronic composition of the vibronic states, and, moreover, about the geometry of the NO2 molecule in the excited state of interest. The results of our analyses are compared with those obtained by other authors. The conclusion arrived at in our previous paper that determining Fermi-constants is useful to help characterize the vibronic bands, is corroborated. In addition, the A rotational constants correspond to geometries that are consistent with the electronic composition of the relevant excited states as expected from the Fermi-constants.
- Subjects :
- JET-COOLED NO2
VISIBLE EXCITATION SPECTRUM
Absorption spectroscopy
EXCITED ELECTRONIC STATES
Chemistry
ROTATIONAL ANALYSIS
General Physics and Astronomy
STATISTICAL-ANALYSIS
Conical intersection
CM(-1)
Spectral line
VIBRONIC LEVELS
Excited state
HYPERFINE-STRUCTURE
ABSORPTION
Vibronic spectroscopy
Physics::Chemical Physics
Physical and Theoretical Chemistry
Atomic physics
BANDS
Ground state
Spectroscopy
Hyperfine structure
Subjects
Details
- Language :
- English
- ISSN :
- 00219606
- Volume :
- 112
- Issue :
- 8
- Database :
- OpenAIRE
- Journal :
- Journal of Chemical Physics
- Accession number :
- edsair.doi.dedup.....4260af1d16266c60310664ca65dc5bb1