Photoelectron Velocity Map Imaging Spectroscopy of Small Beryllium-Containing Anions Open Access

Dermer, Amanda Reed (2017)

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Photoelectron velocity map imaging spectroscopy, also known as slow electron velocity map imaging spectroscopy (SEVI), was used to study small beryllium-containing molecules. The anion to neutral ground state transition, X 2Σ+ → X 1Σ+, of both BeO-and BeS- was studied using a home-built SEVI spectrometer. Rotational constants, electron binding energies, and vibrational intervals were determined experimentally for the first time. The electron binding energy of BeO- and BeS- was found to be 2.174 and 2.248 eV, respectively. Upon rotational analysis, it was seen that both species underwent changes in the molecular rotational angular momenta (ΔN = -1, -2, -3 and -4) when the photodetachment energy was near the detachment threshold. Also observed were dipole-bound state transitions, and for BeS- these transitions (DBS 2Σ+, v′ = 0 - X 2Σ+, v″ = 0) were measured using autodetachment spectroscopy. Predictions made using electronic structure calculations, performed at the RCCSD(T) and MRCI levels of theory, were found to be in reasonable agreement with experimental results for both species.

The BeO- and BeS- produced in the laser ablation source were relatively hot, with several populated vibrational levels (up to v = 3). It was decided that it was necessary to add a quadrupole ion trap to the velocity map imaging system to cool the ions to relatively low temperatures, thus decreasing the population in higher vibrational states. Presented in this report are details regarding the design of the quadrupole ion trap system as well as its basic operating principles.

Table of Contents

Chapter 1: Introduction and Motivation, 1

1.1 Beryllium, Beryllium Clusters, and Beryllium-Containing Molecules, 1

1.2 Photoelectron Velocity Map Imaging Spectroscopy and its Application to Small Beryllium-Containing Molecules, 4

1.3 Perfecting the Velocity Map Imaging Optics, 8 1.4 Organization of the Remaining Thesis,11 1.5 References for Chapter 1, 11

Chapter 2: Photodetachment Spectroscopy of the Beryllium Oxide Anion, BeO-, 19

2.1 Introduction, 19

2.2 Experimental Procedure and Spectrometer Description, 21

2.3 Electronic Structure Calculations, 24

2.4 Experimental Results and Discussion, 29

2.5 Conclusion, 35

2.6 Acknowledgements, 36

2.7 References for Chapter 2, 36

Chapter 3: Photoelectron Velocity Map Imaging Spectroscopy of the Beryllium Sulfide Anion, BeS-, 41

3.1 Introduction, 41 3.2 Experimental Setup, 43 3.3 Theoretical Calculations, 45 3.4 Results and Discussion, 50 3.5 Conclusions, 62 3.6 Acknowledgements, 62 3.7 Reference for Chapter 3, 62

Chapter 4: The Design and Implementation of a 3-Dimmensioanl Cold Ion Trap, 65

4.1 Operating Principles of the Quadrupole Mass Filter, 65

4.2 Operating Principles of the Quadrupole Ion Trap, 70

4.3 Designing the Quadrupole Ion Trap System, 77

4.4 References for Chapter 4, 108

Chapter 5: Conclusion and Future Works, 109

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