Book contents
- Frontmatter
- Contents
- Preface
- List of journal abbreviations
- Part I Foundations of electronic and photoelectron spectroscopy
- Part II Experimental techniques
- Part III Case Studies
- 13 Ultraviolet photoelectron spectrum of CO
- 14 Photoelectron spectra of CO2, OCS, and CS2 in a molecular beam
- 15 Photoelectron spectrum of NO–2
- 16 Laser-induced fluorescence spectroscopy of C3: rotational structure in the 300 nm system
- 17 Photoionization spectrum of diphenylamine: an unusual illustration of the Franck–Condon principle
- 18 Vibrational structure in the electronic spectrum of 1,4-benzodioxan: assignment of low frequency modes
- 19 Vibrationally resolved ultraviolet spectroscopy of propynal
- 20 Rotationally resolved laser excitation spectrum of propynal
- 21 ZEKE spectroscopy of Al(H2O) and Al(D2O)
- 22 Rotationally resolved electronic spectroscopy of the NO free radical
- 23 Vibrationally resolved spectroscopy of Mg+–rare gas complexes
- 24 Rotationally resolved spectroscopy of Mg+–rare gas complexes
- 25 Vibronic coupling in benzene
- 26 REMPI spectroscopy of chlorobenzene
- 27 Spectroscopy of the chlorobenzene cation
- 28 Cavity ringdown spectroscopy of the a1Δ ← X3Σ–g transition in O2
- Appendix A Units in spectroscopy
- Appendix B Electronic structure calculations
- Appendix C Coupling of angular momenta: electronic states
- Appendix D The principles of point group symmetry and group theory
- Appendix E More on electronic configurations and electronic states: degenerate orbitals and the Pauli principle
- Appendix F Nuclear spin statistics
- Appendix G Coupling of angular momenta: Hund's coupling cases
- Appendix H Computational simulation and analysis of rotational structure
- Index
- References
27 - Spectroscopy of the chlorobenzene cation
Published online by Cambridge University Press: 05 June 2012
- Frontmatter
- Contents
- Preface
- List of journal abbreviations
- Part I Foundations of electronic and photoelectron spectroscopy
- Part II Experimental techniques
- Part III Case Studies
- 13 Ultraviolet photoelectron spectrum of CO
- 14 Photoelectron spectra of CO2, OCS, and CS2 in a molecular beam
- 15 Photoelectron spectrum of NO–2
- 16 Laser-induced fluorescence spectroscopy of C3: rotational structure in the 300 nm system
- 17 Photoionization spectrum of diphenylamine: an unusual illustration of the Franck–Condon principle
- 18 Vibrational structure in the electronic spectrum of 1,4-benzodioxan: assignment of low frequency modes
- 19 Vibrationally resolved ultraviolet spectroscopy of propynal
- 20 Rotationally resolved laser excitation spectrum of propynal
- 21 ZEKE spectroscopy of Al(H2O) and Al(D2O)
- 22 Rotationally resolved electronic spectroscopy of the NO free radical
- 23 Vibrationally resolved spectroscopy of Mg+–rare gas complexes
- 24 Rotationally resolved spectroscopy of Mg+–rare gas complexes
- 25 Vibronic coupling in benzene
- 26 REMPI spectroscopy of chlorobenzene
- 27 Spectroscopy of the chlorobenzene cation
- 28 Cavity ringdown spectroscopy of the a1Δ ← X3Σ–g transition in O2
- Appendix A Units in spectroscopy
- Appendix B Electronic structure calculations
- Appendix C Coupling of angular momenta: electronic states
- Appendix D The principles of point group symmetry and group theory
- Appendix E More on electronic configurations and electronic states: degenerate orbitals and the Pauli principle
- Appendix F Nuclear spin statistics
- Appendix G Coupling of angular momenta: Hund's coupling cases
- Appendix H Computational simulation and analysis of rotational structure
- Index
- References
Summary
Concepts illustrated: ZEKE spectroscopy; MATI spectroscopy; vibrational structure and the Franck–Condon principle; ab initio calculations; vibronic coupling; Fermi resonance.
The lowering of symmetry in moving from benzene (D6h) to chlorobenzene (C2v) results in the removal of molecular orbital degeneracies. A convenient way of investigating this effect is through conventional photoelectron spectroscopy, and indeed Ruščić et al. studied this degeneracy breaking in 1981 using both HeI and HeII photoelectron spectroscopy [1]. The spectra obtained are shown in Figure 27.1, with the upper trace being that recorded using HeI radiation and the lower trace using HeII radiation.
The first two bands have similar ionization energies (maxima at 9.07 and 9.54 eV) and almost identical intensities. These bands correlate with the two components of the e1g HOMO in benzene, which is a pair of π bonding orbitals (see Chapter 25) but which have split into two distinct orbitals in chlorobenzene owing to the lowering of the symmetry. Note that these two bands, and indeed most other bands in the spectra, are relatively broad. The next highest bands again form a pair, but these have considerably sharper profiles and correspond to ionization from lone pairs on the Cl atom.
The low resolution in conventional photoelectron spectroscopy restricts the amount of information that can be extracted. In this Case Study we consider alternative techniques that provide additional information about the chlorobenzene cation. This builds upon the material encountered in the previous two Case Studies.
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- Electronic and Photoelectron SpectroscopyFundamentals and Case Studies, pp. 216 - 222Publisher: Cambridge University PressPrint publication year: 2005