Journal article
The ionic states of difluoromethane: A reappraisal of the low energy photoelectron spectrum including ab initio configuration interaction computations
The Journal of chemical physics, Vol.147(7), pp.074305-074305
08/21/2017
Handle:
https://hdl.handle.net/2376/108971
PMID: 28830186
Abstract
A new synchrotron-based study of the photoelectron spectrum (PES) of difluoromethane is interpreted by an ab initio analysis of the ionic states, which includes Franck-Condon (FC) factors. Double differentiation of the spectrum leads to significant spectral sharpening; the vibrational structure observed is now measured with greater accuracy than in previous studies. Several electronic structure methods are used, including equation of motion coupled cluster calculations with single and double excitations (EOM-CCSD), its ionization potential variant EOM-IP-CCSD, 4th order Møller-Plesset perturbation theory (MP4SDQ) configuration interaction (CI), and complete active space self-consistent-field (CASSCF) methods. The adiabatic ionization energies (AIEs) confirm the assignments as band I, one state 1
B
(12.671 eV); band II, three states, 1
B
(14.259) < 1
A
(15.030) < 1
A
(15.478 eV); and band III, three states, 2
B
(18.055) < 2
A
(18.257) < 2
B
(18.808 eV). The three ionizations in each of the bands II and III lead to selective line broadening of the PES structure, which is attributed to vibronic overlap. The apparent lack of a vibrational structure attributable to both the 1
A
and 2
A
states in the PES arises from line broadening with the preceding states 1
B
and 2
B
, respectively. Although these
A
states clearly overlap with their adjacent higher IE, some vibrational structure is observed on the higher IE. The effects of vibronic coupling are evident since the observed structure does not fit closely with the calculated Born-Oppenheimer FC profiles. Correlation of the lowest group of four AIEs in the PES of other members of the CH
X
group, where X = F, Cl, Br, and I, clearly indicate these effects are more general.
Metrics
4 Record Views
Details
- Title
- The ionic states of difluoromethane: A reappraisal of the low energy photoelectron spectrum including ab initio configuration interaction computations
- Creators
- Michael H Palmer - School of Chemistry, University of Edinburgh, Joseph Black Building, David Brewster Road, Edinburgh EH9 3FJ, Scotland, United KingdomMalgorzata Biczysko - International Centre for Quantum and Molecular Structures, College of Sciences, Shanghai University, 99 Shangda Road, Shanghai 200444, ChinaAlberto Baiardi - Scuola Normale Superiore, Piazza Cavalieri 7, 56126 Pisa, ItalyMarcello Coreno - ISM-CNR, Istituto di Struttura della Materia, LD2 Unit, 34149 Trieste, ItalyMonica de Simone - CNR-IOM Laboratorio TASC, Trieste, ItalyCesare Grazioli - ISM-CNR, Istituto di Struttura della Materia, LD2 Unit, 34149 Trieste, ItalySøren Vrønning Hoffmann - ISA, Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, DK-8000 Aarhus C, DenmarkNykola C Jones - ISA, Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, DK-8000 Aarhus C, DenmarkKirk A Peterson - Department of Chemistry, Washington State University, Pullman, Washington 99164-4630, USA
- Publication Details
- The Journal of chemical physics, Vol.147(7), pp.074305-074305
- Academic Unit
- Chemistry, Department of
- Publisher
- United States
- Identifiers
- 99900547133001842
- Language
- English
- Resource Type
- Journal article