Electronic and Photoionization Spectroscopy of Heavy Metal-Containing Diatomic Molecules Open Access

Bartlett, Joshua H. (2016)

Permanent URL: https://etd.library.emory.edu/concern/etds/n870zr298?locale=en


Gas phase molecules ThS, ThCl, SmO, BaO, and BaCl have been investigated using laser-induced fluorescence (LIF), dispersed fluorescence (DF), resonant multi-photon ionization (REMPI), two-color photoionization efficiency (PIE), and two-color pulsed field ionization zero kinetic energy photoelectron (PFI-ZEKE) spectroscopy. ThS and ThCl have been studied out of interest in the behavior of the actinide (Ac) - 3p compounds. In previous experiments, the Ac - 2p compounds ThN, ThO, and ThF have been studied. Extension of these studies to ThS and ThCl is an important foundational step for unraveling the structure of more complex actinide molecules. These molecules are also difficult to address with computational methods, and the spectroscopic data are used to evaluate performance of various levels of electronic structure theory. Ground state constants, excited state term energies, and excited state constants are found using the above techniques and reported for both the neutral molecule and its cation. SmO+ was predicted to form spontaneously in oxygen-rich environments when Sm vapor oxidizes, accompanied by electron emission. A high-altitude atmospheric release of Sm did not succeed in detecting an increase in electron density. The predictions were based on thermochemical data which were subsequently reevaluated. Photoionization experiments revealed that the ionization energy of SmO was underestimated by about 3%. The low electron density is partially explained by this result. BaO and BaCl are molecular species that can be formed from ultracold atomic ions in magneto-optical traps. Ultracold molecules are a unique platform that can be useful for many unique experiments, such as measurement of fundamental physical constants, but manipulation of the ultracold molecules cannot proceed without measurement of the ion molecular constants and excited state term energies. Ionization energy, vibration frequency, and excited state term energies are investigated and reported for both molecules.

Table of Contents

Chapter 1. Introduction 1

References 6

Chapter 2. Spectroscopic and Theoretical Investigations of ThS and ThS+ 8

2.1. Introduction 8

2.2. Experimental Methods 10

2.2.1. Notation 12

2.2.2. Electronic Structure Calculations 12

2.3. Experimental Results 16

2.4. Discussion 19

References 24

Chapter 3. Spectroscopic and Theoretical Measurements of the Low-Lying States of ThCl and ThCl+ 38

3.1. Introduction 38

3.1.1. Notation 41

3.2. Experimental 41

3.2.1. Computational Treatment of Ground and Low-Lying Excited States 45

3.2.2. Ab Initio Composite Treatment for the IP of ThCl 47

3.3. Results and Discussion 49

3.4. Summary 53

References 55

Chapter 4. Evaluation of the Exothermicity of the Chemi-ionization Reaction Sm + O → SmO+ + e- 69

4.1. Introduction 69

4.2. Experimental and Theoretical Methods 74

4.2.1. SIFT Apparatus 74

4.2.2. Guided Ion Beam Tandem Mass Spectrometer 75

4.2.3. GIBMS Data Analysis 77

4.2.4. REMPI and PFI-ZEKE 78

4.3. Experimental Results 80

4.3.1. SIFT 80

4.3.2. GIBMS 82 Sm+ + LO (L = O, SO, C) 82 SmO+ + Xe/O2 85

4.3.3. REMPI and PFI-ZEKE 86

4.4. Thermochemical Results 89

4.4.1. SmO+ 89

4.4.2. Other Thermochemical Results 91

4.5. Discussion 92

4.5.1. Chemi-ionization Reaction 92

4.6. Conclusion 94

References 96

Chapter 5. Spectroscopic and Theoretical Studies of the Low-Lying States of BaO+ 114

5.1. Introduction 114

5.2. Experimental 116

5.3. Results 118

5.3.1. Electronic Structure Calculations 120

5.3.2. Data Analysis 123

5.4. Discussion 125

References 128

Chapter 6. Characterization of the BaCl+ (X1Σ+) Cation by Photoelectron Spectroscopy 142

6.1. Introduction 142

6.2. Experimental 144

6.3. Results and Discussion 145

References 148

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