Electronic Structure of Metal-Containing Diatomic Ions Open Access

VanGundy, Robert (Fall 2018)

Permanent URL: https://etd.library.emory.edu/concern/etds/2f75r915n?locale=en


Investigation of eight neutral molecules and their ions, SmO, NdO, ThCl, UN, BaO, BaCl, CaO, and CaOH+ using gas phase spectroscopy will be described. These molecules have been studied using a combination of the following spectroscopic techniques: laser-induced fluorescence (LIF), dispersed fluorescene (DF), resonant multiphoton ionization (REMPI), photoionization efficiency (PIE), pulsed-field ionization zero kinetic energy (PFI-ZEKE) photoelectron spectroscopy.

Previous literature values suggests the chemi-ionization reaction proceeds spontaneously for both samarium and neodymium. In an effort to increase electron density in the ionosphere Air Force Research Laboratory (AFRL) is interested in test releases of both samarium and neodymium. Following samarium releases, the magnitude of electron density created was two orders of magnitude lower than expected. A reevaluation of the thermochemical data was performed. Determination of the ionization energy of SmO contributed to understanding the samarium chemi-ionization reaction, and the lower observed electron density. A proactive reevaluation of the neodymium thermochemical data was performed to advise AFRL on the suitability of Nd test releases. Determination of the ionization energy of NdO contributes to the suggestion that Nd is a good candidate for these test. The low-lying transition of NdO+ are also reported.

The first gas-phase spectroscopic studies on ThCl, ThCl+, and UN+ identify constants for the ground state, as well as term energies for low-lying excited electronic states. Theoretical treatment of actinides is difficult and experimental observation of predicted transitions provides an indication of the accuracy of current high-level computational methods, as well as a benchmark for further development of theoretical models.

Alkaline-earth ions are isoelectronic to the alkali metals. Therefore, well-studied laser cooling schemes to create ultracold alkali atoms can be adjusted for these alkaline-earth ions. The electric charge allows for trapping via rf fields and further experimentation. These atoms are trapped in a coulomb crystal and molecular ions can be created in these traps by addition of a reactant gas. Knowledge of the ionic transitions of these created molecules is necessary to determine the temperature of these molecules. The low-lying states of BaO+, BaCl+, and CaO+ are reported, and compared to current theoretical treatments. Attempts to investigate CaOH+ as well as miscellaneous laboratory contributions are also described.

Table of Contents

Chapter 1.1. Introduction                                                                                                        1

              1.2. References                                                                                                          5

Chapter 2.   Evaluation of the Exothermicity of the Chemi-ionization Reaction         7

                      Sm + O → SmO+ + e-

              2.1. Introduction                                                                                                         7

              2.2. Experimental and Theoretical Methods                                                             11

                      2.2.1. SIFT Apparatus                                                                                       11

                      2.2.2. Guided Ion Beam Tandem Mass Spectrometer                                       12

                      2.2.3. GIBMS Data Analysis                                                                             14

                      2.2.4. REMPI and PFI-ZEKE                                                                            15

              2.3. Experimental Results                                                                                         16

                      2.3.1. SIFT                                                                                                         16

                      2.3.2. GIBMS                                                                                                    18

                            Sm+ + LO (L = O, SO, C)                                                      18

                            SmO+ + Xe/O2                                                                        22

                      2.3.3. REMPI and PFI-ZEKE                                                                            22

              2.4. Thermochemical Results                                                                                    25

                      2.4.1. SmO+                                                                                                       25

                      2.4.2. Other Thermochemical Results                                                                27

              2.5. Discussion                                                                                                         28

                      2.5.1. Chemi-Ionization Reaction                                                                      28

              2.6. Conclusion                                                                                                         30

              2.7. References                                                                                                         31

Chapter 3.   Probing the Electronic Structure of NdO+                                                   49

              3.1. Introduction                                                                                                      49

              3.2. Experimental Details                                                                                          51

              3.3. Results and Discussion                                                                                       53

              3.4. Conclusion                                                                                                         56

              3.5. References                                                                                                         58

Chapter 4.   Spectroscopic and Theoretical Studies of ThCl and ThCl+                     65

              4.1. Introduction                                                                                                      65

              4.2. Computational Treatment of Ground and Lowy-Lying Excited             67

                      States of ThCl and ThCl+

              4.3. Experiment                                                                                                        71

              4.4. Experimental Results and Analyses                                                              73

              4.5. Discussion                                                                                                         76

              4.6 Conclusion                                                                                                         79

              4.7. References                                                                                                         81

Chapter 5.   Spectroscopy of the Low-Lying States of UN+                                          93

              5.1. Introduction                                                                                                      93

              5.2. Experiment                                                                                                        95

              5.3. Results                                                                                                               96

              5.4. Analysis and Discussion                                                                                 98

              5.5. Conclusion                                                                                                         101

              5.6. References                                                                                                         102

Chapter 6.    Spectroscopy and Theoretical Studies of the Low-Lying States of BaO+         109

              6.1. Introduction                                                                                                      109

              6.2. Experimental                                                                                                     111

              6.3. Results                                                                                                               112

              6.4. Electronic Structure Calculations                                                                 114

              6.5. Data Analysis                                                                                                     117

              6.6. Discussion                                                                                                         118

              6.7. References                                                                                                         122

Chapter 7.   Characterization of the BaCl+(X1Σ+) Cation by Photoelectron Spectroscopy   136

              7.1. Introduction                                                                                                      136

              7.2. Experimental                                                                                                     137

              7.3. Results and Discussion                                                                                    138

              7.4. References                                                                                                         141

Chapter 8.   Spectroscopy of the Low-Lying States of CaO+                                         147

              8.1. Introduction                                                                                                      147

              8.2. Experimental                                                                                                     149

              8.3. Results                                                                                                               150

              8.4. References                                                                                                         156

Chapter 9.    Miscellaneous and Uncompleted                                                               165

              9.1. Introduction                                                                                                      165

              9.2. Experimental Details and Results for CaOH+                                              166

              9.3. Continuum ND6000 Repair                                                                             167

              9.4. Source Motor Redesign and Wiring                                                                168

              9.5. References                                                                                                          171

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