Some Pattern Recognition Considerations for Low-Temperature Luminescence and Room Temperature Fluorescence Spectra

Abstract

Low-temperature (77 K) luminescence (LTL) and room temperature fluorescence (RTF) spectra of polynuclear aromatic hydrocarbons with varying amounts of spectral structure are studied as a function of several instrument parameters (emission slit width, scan speed, and damping) in order to develop quantitative criteria for spectral quality and reproducibility. The purpose of this study is to assess the classification and pattern recognition capabilities for hazardous chemicals for various spectral techniques and to develop suitable spectral libraries and search routines. In order to quantitate the effect of the instrument parameters on the spectrum, a statistic (power) was used to measure spectral quality. In addition, three measures of similarity, used for assessing the agreement between two patterns (spectra), were evaluated to determine the variability that can be expected in spectra obtained under the same and different instrumental conditions. Analysis of the data confirms that the low-temperature luminescence technique produces better quality spectra than the room temperature fluorescence technique, but that room temperature fluorescence spectra are more repeatable.