New techniques for sub-Doppler spectroscopy of molecular ions

This thesis details research in developing new methods for performing high-resolution sub-Doppler spectroscopy of molecular ions in the laboratory. Molecular ions are of interest to a variety of fields, from astrochemistry to fundamental physics to the study of chemical reactive intermediates. The limiting factor in developing a deeper understanding of many ion systems is the quality of the available laboratory spectra. Traditional techniques for high-resolution spectroscopy of ions are limited by two factors: the precision is often limited by the Doppler-broadened linewidths of the observed spectra, and the accuracy is typically limited by the laser frequency calibration. Two new techniques are described in this thesis: cavity enhanced velocity modulation spectroscopy (CEVMS) and ion beam spectroscopy. Each of these techniques was first implemented in the near-infrared spectral region using a titanium sapphire laser, and was then extended into the mid-infrared, using an optical parametric oscillator (OPO) for CEVMS and difference frequency generation (DFG) for the ion beam. Both of these techniques allow for sub-Doppler resolution to significantly improve the precision beyond what was possible with traditional ion spectroscopy, and because both techniques are based on direct absorption spectroscopy, they require nothing of the ion of interest other than an allowed transition within the tuning range of the laser used, making them applicable to a wide variety of ions. The lasers used with both of these techniques have been referenced with an optical frequency comb for sub-megahertz absolute calibration accuracy of linecenters, which is a significant improvement beyond the 20-200 MHz accuracy that was typical of ion spectroscopy before the work presented in this thesis.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Chemistry

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2013

Author dc:creator

• Siller, Brian

Contributors dc:contributor

• McCall, Benjamin J.
• Gruebele, Martin
• Lisy, James M.
• Scheeline, Alexander

• spectroscopy
• infrared
• molecular ion
• sub-doppler
• ion beam
• velocity modulation

Statement dc:rights

• Copyright 2013 Brian M. Siller

Language dc:language

en

Handle dc:identifier

http://hdl.handle.net/2142/44338

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/44338