Spectrometric Studies of Selected Nitrocompounds Using Laser-Induced Photofragmentation/Photoionization at 193 nm.
Abstract
A new method for detection trace vapors of NO2 containing compounds near atmospheric conditions has been demonstrated using one color laser photofragmentation/fragment ionization spectrometry. An ArF laser is employed to both photolytically fragment the target molecules in a collision-free environment and ionize the characteristic NO fragments. The production of NO is hypothesized to result from a combination of two NO2 unimolecular fragmentation pathways, one yielding NO in its X(2)Pi electronic ground state and the other in its A(2)Sigma+ excited state. Ionization of ground state NO molecules is accomplished by resonance-enhanced multiphoton ionization processes via their A(2)Sigma <-X(2)Pi (3,0), B(2)Pi <-X(2)Pi (7,0), and/or D(2)Sigma+ <- X(2)Pi (0,1) bands at 193 nm. The analytical utility of this method is demonstrated in a molecular beam time-of-flight apparatus. Limits of detection range from the parts-per-million (ppm) to parts-per-billion (ppb) level for NO, NO2, CH3NO2, dimethylnitramine (DMNA), ortho- and meta-nitrotoluene, nitrobenzene, and trinitrotoluene (TNT). Under effusive beam experimental conditions, discrimination between structural isomers, ortho-nitrotoluene and meta-nitrotoluene, has been demonstrated with the use of their characteristic photofragmentation/photoionization mass spectra. (jg)
Document Details
- Document Type
- Technical Report
- Publication Date
- Nov 01, 1994
- Accession Number
- ADA289947
Entities
People
- George W. Lemire
- Josef B. Simeonsson
- Rosario C. Sausa
Organizations
- United States Army Research Laboratory