Browse All

Theses & Dissertations

Submissions

  • Submissions (Articles, Chapters, and other finished products)

Constructing velocity distributions in crossed-molecular beam studies using fourier transform doppler spectroscopy

UNCG Author/Contributor (non-UNCG co-authors, if there are any, appear on document)
Josué Roberto Monge (Creator)
Institution
The University of North Carolina at Greensboro (UNCG )
Web Site: http://library.uncg.edu/
Advisor
Liam Duffy

Abstract: The goal of our scattering experiments is to derive the distribution the differential cross-section and elucidate the dynamics of a bimolecular collision via pure rotational spectroscopy. We have explored the use of a data reduction model to directly transform rotational line shapes into the differential cross section and speed distribution of a reactive bimolecular collision. This inversion technique, known as Fourier Transform Doppler Spectroscopy (FTDS), initially developed by James Kinsey [1], deconvolves the velocity information contained in one-dimensional Doppler Profiles to construct the non-thermal, state-selective three-dimensional velocity distribution. By employing an expansion in classical orthogonal polynomials, the integral transform in FTDS can be simplified into a set of purely algebraic expressions technique; i.e. the Taatjes method [2]. In this investigation, we extend the Taatjes method for general use in recovering asymmetric velocity distributions. We have also constructed a hypothet- ical asymmetric distribution from adiabatic scattering in Argon-Argon to test the general method. The angle- and speed-components of the sample distribution were derived classically from a Lennard-Jones 6-12 potential, with collisions at 60 meV, and mapped onto Radon space to generate a set of discrete Doppler profiles. The sample distribution was reconstructed from these profiles using FTDS. Both distributions were compared along with derived total cross sections for the Argon-Argon system. This study serves as a template for constructing velocity distributions from bimolecular scattering experiments using the FTDS inversion technique.

Additional Information

Publication
Thesis
Language: English
Date: 2012
Keywords
Crossed-Molecular Beam Studies, Differential Cross Section, Fourier Transform Doppler Spectroscopy, FTDS, Tomographic Reconstruction, Velocity Distribution
Subjects
Molecular spectroscopy
Molecular beams $x Scattering
Bimolecular collisions