A Journey towards the Construction and Operation of a Photoelectron Velocity-Map Imaging Spectrometer Open Access

Mascaritolo, Kyle (2016)

Permanent URL: https://etd.library.emory.edu/concern/etds/4t64gn68z?locale=en


Photoelectron velocity-map imaging spectroscopy is a highly versatile spectroscopic technique that is capable of measuring numerous molecular properties of neutral and anionic gas phase species. Presented here is a report of the evolution of a spectrometer capable of studying beryllium containing molecules with the use of photoelectron velocity - map imaging spectroscopy. During the development of the spectrometer, several sub-projects were executed to benchmark its performance. The 2Π(4p)-X 2Π(3p) band system of the AlAr van der Waals complex using two-photon excitation was first studied to measure the production of internally cold molecules from the laser ablation source. With the determination that cold molecules could be produced, the radical BeOH was studied. The ground state of BeOH was predicted to have a bent equilibrium structure, contrary to the other alkaline earth metal hydroxides with linear equilibrium ground state geometries. The use of laser excitation techniques to observe the 22A'-12A' transition of BeOH/D in the energy range 30300-32800 cm-1 revealed rotationally resolved spectra of several bending mode transitions. Ab initio calculations were used to guide the analysis of the spectroscopic data permitting unambiguous assignment of all spectral features. It was confirmed that the equilibrium geometry of the ground state is bent, and that the barrier to linearity lies below the zero-point energies for both BeOH and BeOD. A new Wiley-McLaren time of flight mass spectrometer was then incorporated into the existing spectrometer to provide the ability to mass separate anions generated from the laser ablation source. The 1Σ+ ← X 1Σ+ ground state to dipole bound state electronic transition of AlO anion was studied by means of autodetachment spectroscopy. This studied benchmarked the capability to photodetach mass separated anions. Lastly, velocity - map imaging optics and a position sensitive detector were added to the spectrometer to finalize the construction of the photoelectron velocity - map imaging spectrometer. The previously unreported X 1Σ+ -X 2Σ+ anion ground state to neutral ground state electronic transition of BeO- anion was studied as a benchmark molecule for the spectrometer. The current results are presented here, along with a detailed report of the individual components of the spectrometer, and an overall evaluation of the performance of the spectrometer.

Table of Contents

Chapter 1: A Journey towards the Construction and Operation of a Photoelectron Velocity-Map Imaging Spectrometer. 1

1.1 Photoelectron Velocity - Map Imaging Spectroscopy: Application to the Study of Beryllium Containing Clusters. 2

1.2 The First Stage - AlAr. 4

1.3 BeOH in the First Stage. 7

1.4 Anions and Photodetachment in Stage Two. 8

1.5 The Final Stage. 13

1.6 Developing High Quality Velocity - Map Imaging Optics. 22

1.7 Structure of the Remaining Dissertation. 25

1.8 References to Chapter 1. 28

Chapter 2: Two-photon excitation of the 2Π(4p)-X2Π(3p) transition of AlAr. 36

2.1 Introduction. 36

2.2 Experimental. 37

2.3 Results and Discussion. 38

2.4 Postscript. 44

2.5 Acknowledgement. 44

2.6 References to Chapter 2. 45

Chapter 3: Experimental and Theoretical Characterization of the 22A'-12A' Transition of BeOH/D. 46

3.1 Introduction. 47

3.2 Experimental. 49

3.3 Theoretical Calculations. 51

3.4 Experimental Results and Analyses. 62

3.5 Discussion. 75

3.6 Conclusion. 78

3.7 Acknowledgements. 79

3.8 References to Chapter 3. 80

Chapter 4: Autodetachment Spectroscopy of the Aluminum Oxide Anion Dipole Bound State. 83

4.1 Introduction. 83

4.2 Experimental. 86

4.3 Experimental Results and Analysis. 89

4.4 Electronic Structure Calculations. 92

4.5 Discussion. 95

4.6 Conclusion. 103

4.7 Acknowledgement. 103

4.8 References to Chapter 4. 104

Chapter 5: Photoelectron Velocity-Map Imaging of the Beryllium Oxide Anion. 107

5.1 Introduction. 107

5.2 Experimental Procedure and Photoelectron Velocity - Map Imaging Spectroscopy. 109

5.3 Electronic Structure Calculations. 114

5.4 Calibration with Sulfur Anion, S. 117

5.5 Results and Discussion. 121

5.6 Image Quality and its Effects on Spectrometer Resolution. 129

5.7 Conclusion. 132

5.8 References to Chapter 5. 134

Conclusion to Dissertation. 137

About this Dissertation

Rights statement
  • Permission granted by the author to include this thesis or dissertation in this repository. All rights reserved by the author. Please contact the author for information regarding the reproduction and use of this thesis or dissertation.
  • English
Research Field
Committee Chair / Thesis Advisor
Committee Members
Last modified

Primary PDF

Supplemental Files