Negative Ion Photoelectron Spectroscopy Confirms the Prediction of a Singlet Ground State for the 1,8-Naphthoquinone Diradical
Negative ion photoelectron (NIPE) spectra, with 193, 266, 300, and 355 nm photons, of the radical anion of 1,8-naphthoquinone (1,8-NQ•-) have been obtained at 20K. The electron affinity of 1,8-NQ is determined from the first resolved peak in the NIPE spectrum to be 2.98 ± 0.04 eV. Franck-Condon factors (FCFs), calculated from the CASPT2/aug-cc-pVDZ optimized geometries, normal modes, and vibrational frequencies successfully simulate the intensity and frequencies of the spectral features that are associated with the lowest two electronic states. Here, the NIPE spectra of 1,8-NQ•- and the peak assignments, based on the computed FCFs, confirm the theoretical predictions that 1A1 is the ground state of 1,8- NQ and that 3B2 is the first excited state. The spectra provide an experimental value of ΔEST = -1.5 kcal/mol, which is within about 1 kcal/mol of the (12/12)CASPT2/aug-cc-pVTZ calculated value of ΔEST = -2.6 kcal/mol.
- Research Organization:
- Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
- Sponsoring Organization:
- USDOE
- Grant/Contract Number:
- AC05-76RL01830
- OSTI ID:
- 1530598
- Report Number(s):
- PNNL-SA-139614
- Journal Information:
- Journal of Physical Chemistry. A, Molecules, Spectroscopy, Kinetics, Environment, and General Theory, Vol. 123, Issue 14; ISSN 1089-5639
- Publisher:
- American Chemical SocietyCopyright Statement
- Country of Publication:
- United States
- Language:
- English
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