Spectroscopic studies of molecules that challenge computational chemistry Público
Antonov, Ivan Olegovich (2013)
Abstract
The gas-phase electronic spectra of small Be-containing (Be2+, BeOBe+, BeC), Hf-containing (HfF+ and HfS+) and actinide molecules (ThF, ThF+, UF and UF+) were recorded with variety of experimental techniques. Ab initio electronic structure calculations were used to facilitate the assignment of the observed spectra.
The ground electronic states of Be2+ and BeOBe+ were probed using the PFI-ZEKE technique. The rotational symmetry selection rules were used to confirm the symmetry of the ground state as 2Σu in Be2+ and 2Σg+ in BeOBe+. The ionization energies were refined over previous measurements. Results from recent theoretical calculations are in good agreement with the experimental data.
Electronic spectra for BeC were recorded over the range 30500-40000 cm-1. The vibronic structure consists of a series of bands with erratic energy spacings. Theoretical calculations indicate that the erratic vibronic structure results from strong interactions between the four lowest energy 3Π states. The predictions were sufficiently close to the observed structure to permit partial assignment of the spectra. Bands originating from the low-lying 15Σ- state were also identified, yielding a 5Σ- to X3Σ- energy interval of 2305±80 cm-1.
The electronic spectra for HfS+ and HfF+ were recorded with PFI-ZEKE technique. Three electronic states were identified in HfS+ and four in HfF+. The ionization energies for neutral molecules, term energies and molecular constants for the ground and low-lying states of cations are reported. The results for HfF+ support the contention that HfF+ is a viable candidate for electron electric dipole moment measurements. The spacings between adjacent X1Σ+ and 3Δ1levels are found to be less favorable for the proposed studies of the fine structure constant.
The low-lying states of ThF+ and UF+ were probed PFI-ZEKE photoelectron spectroscopy. Vibronic progressions belonging to four electronic states of ThF+ and sixteen electronic states of UF+ were identified. The ground state in ThF+ is tentatively assigned as 1Σ+. The 3Δ1 state of ThF+, of interest for investigation of the electron electric dipole moment, is just 315.0(5) cm-1 above the ground state. The observed patterns of low-lying electronic states of UF+ are consistent with ab initio calculations and ligand field theory predictions.
Table of Contents
CHAPTER I. INTRODUCTION 1
REFERENCES 6
CHAPTER II. SPECTROSCOPIC CHARACTERIZATION OF Be2+ X 2Σu+ AND THE IONIZATION ENERGY OF Be2 8
II.1 INTRODUCTION 8
II.2 EXPERIMENTAL 9
II.3 RESULTS AND ANALYSIS 12
II.4 DISCUSSION 13
REFERENCES 16
CHAPTER III. PFI-ZEKE SPECTRUM OF THE GROUND ELECTRONIC STATE OF BEOBE+ 25
III.1 INTRODUCTION 25
III.2 EXPERIMENTAL 26
III.3 RESULTS AND ANALYSIS 28
III.4 DISCUSSION 29
REFERENCES 31
CHAPTER IV. EXPERIMENTAL AND THEORETICAL STUDIES OF THE ELECTRONIC TRANSITIONS OF BEC 38
IV.1 INTRODUCTION 38
IV.2 THEORETICAL CALCULATIONS 40
IV.3 EXPERIMENTAL 42
IV.4 RESULTS AND ANALYSIS 44
IV.5 DISCUSSION 46
REFERENCES 51
CHAPTER V. LOW-LYING STATES OF HFS+ AND THE IONIZATION ENERGY OF HFS 70
V.1 INTRODUCTION 70
V.2 EXPERIMENTAL 71
V.3 AB INITIO CALCULATIONS 73
V.4 EXPERIMENTAL RESULTS 74
V.5 DISCUSSION 78
REFERENCES 80
CHAPTER VI. SPECTROSCOPIC INVESTIGATIONS OF ThF, ThF+ AND HfF+ 90
VI.1 INTRODUCTION 90
VI.2 EXPERIMENTAL METHOD 92
VI.3 NOTATION 94
VI.4 RESULTS 94
VI.4.1 SPECTROSCOPY OF HFF+ 94
VI.4.2 REMPI AND LIF SPECTRA OF NEUTRAL THF 96
VI.4.3 MEASUREMENT OF THE THF IONIZATION ENERGY AND THE
SPECTROSCOPY OF THF+ 98
VI.5 ELECTRONIC STRUCTURE CALCULATIONS OF THF
AND THF+ 103
VI.6 DISCUSSION 105
VI.6.1 HFF+ SPECTRAL ASSIGNMENT
105
VI.6.2 THF AND THF+ SPECTRAL ASSIGNMENT 106
VI.6.3 IONIZATION AND BOND DISSOCIATION ENERGIES 108
REFERENCES 109
CHAPTER VII. SPECTROSCOPIC AND THEORETICAL INVESTIGATIONS OF UF AND UF+ 131
VII.1 INTRODUCTION 131
VII.2 EXPERIMENTAL 133
VII.3 NOTATION 135
VII.4 CALCULATIONS 135
VII.5 RESULTS 137
VII.6 ANALYSIS AND DISCUSSION 139
VII.6.1 UF 139
VII.6.2 UF+ 142
VII.7 CONCLUSIONS 147
REFERENCES 148
APPENDIX. SUPPLEMENTARY MATERIAL ON BeC CALCULATIONS 167
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