Negative Ion Photoelectron Imaging Spectroscopy of Iodine Monobromide and Copper Hydrides

Author
Abstract
<p>This thesis contains the results of several negative ion photoelectron spectroscopy experiments performed on two types of anions. The first class of anions studied consisted of copper containing complexes, including CuH<sup>-</sup>, CuD<sup>-</sup>, CuH<sub>2</sub><sup>-</sup>, CuD<sub>2</sub><sup>-</sup>, and CuCD<sub>3</sub>O<sup>-</sup>. The photoelectron spectra of these molecules allowed us to measure (for the first time) the electron-binding energies of the ground and excited states of the neutrals as well as the electron affinities when possible. Franck-Condon simulations were performed on the molecules to determine the bond length change between the anion and neutral. A predicted but until now unobserved, <strong>a</strong> <sup>3</sup>Σ<sup>+</sup> excited state of CuH and CuD is seen in the anion spectra; the electron affinity is measured as 0.444(6) eV for CuH. The spectra of CuH<sub>2</sub><sup>-</sup> and CuD<sub>2</sub><sup>-</sup> allow us to study the neutrals for the first time; two geometric isomers are present in the spectra. The CuH<sub>2</sub><sup>-</sup> photoelectron spectrum is dominated by a strong transition to the linear excited <sup>2</sup>Σ<sub>g</sub> state and accompanied by an extended weak-unresolved vibrational progression involving the bent ground <sup>2</sup>B<sub>2</sub> state. <em>Ab initio </em>calculations of the 0.255 eV energy difference between these two states show EA(CuH<sub>2</sub>) to be 2.60(5) eV. Copper methoxy is only briefly presented as a detailed analysis will follow in a subsequent publication; however, a measured electron affinity of 1.077 eV is determined for this molecule from the photoelectron spectra presented here.</p> <p>The second type of molecule studied is the heterodiatom IBr. The photoelectron spectra of the IBr anion are characterized by three distinct electronic states. An extended vibrational progression is present for the ground state in the neutral, which lacked a distinct origin; it is caused by a shortening of the bond length between the anion and the neutral. Several excited states are present in the spectra, providing confirmation to previous experimental results. The IBr<sup>-</sup> photoelectron spectrum exhibits transitions to the ground (<strong>X</strong> <sup>1</sup>Σ) and lowest-excited triplet <strong>A</strong> <sup>3</sup>Π<sub>1</sub> and <strong>A</strong> <sup>3</sup>Π<sub>2</sub> states. Previous experimental results of the term-splitting energy between the ground <sup>1</sup>Σ and excited <sup>3</sup>Π<sub>1</sub> states of 1.525 eV give an electron affinity of 2.51(1) eV. The vibrational progression observed in the excited states matches extremely well to previous results, confirming the correct identification of the electronic states.</p>
Year of Publication
2007
University
University of Colorado Boulder
City
Boulder
Advisors - JILA Fellows
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