Studies of the analytical utility of low-temperature photoacoustic spectroscopy
The present study investigated the analytical utility of laser-excited, low-temperature photoacoustic (PA) spectroscopy, particularly for the detection of weakly fluorescing and non-fluorescing polycyclic aromatic compounds (PACs) isolated in low-temperature (5 to 20 K) vapor deposited matrices. Photoacoustic spectroscopy of other low-temperature samples was also studied. In order to accomplish this objective, piezoelectric (PE) transducers were evaluated as low-temperature PA detectors. Two PE materials were studied, X-cut crystalline quartz and lead-zirconate-titanate (PZT). PZT was found to exhibit approx.10 times higher sensitivity. PA spectra of Nd(OH)/sub 3/ powder at 6 to 8 K were taken to demonstrate the ability to acquire piezoelectrically-detected PA spectra at low-temperatures. Laser-excited PA spectra were recorded for a number of matrix-isolated PACs. The detection limits were 500 ng for quinoline and 50 ng for pyrene. Both of these mass detection limits corresponded to a limiting detectable thermal energy liberated of approx.175 nJ. Singlet-triplet intersystem crossing was determined to be the primary source of the liberated thermal energy which generates the PA signal. The S/sub 1/-T/sub 1/ energy gap is approx.30 to 40% of the total S/sub n/-S/sub o/ energy gap (i.e., the absorbed photon energy) for most PACs. The main limitation to the analytical utility of the technique was that most of the non- and weakly-fluorescing PACs studied did not yield highly resolved spectra when matrix isolated. This fact adversely affected the ability to identify individual compounds in multi-component samples. A detector was developed for obtaining PA spectra of samples in frozen solutions at 77 K. Laser-excited PA spectra of Nd(OH)/sub 3/ powder dispersed in low-temperature glasses (isopropanol and glycerine/H/sub 2/O) were obtained. 119 refs., 39 figs., 7 tabs.
- Research Organization:
- Tennessee Univ., Knoxville (USA)
- DOE Contract Number:
- AC05-76OR00033; AC05-84OR21400
- OSTI ID:
- 5563525
- Report Number(s):
- DOE/OR/00033-101; ON: DE85015020
- Resource Relation:
- Other Information: Thesis
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
NEODYMIUM HYDROXIDES
PHOTOACOUSTIC SPECTROSCOPY
POLYCYCLIC AROMATIC HYDROCARBONS
TRANSDUCERS
EVALUATION
DYE LASERS
EXCITATION
EXPERIMENTAL DATA
LASER RADIATION
LEAD COMPOUNDS
PIEZOELECTRICITY
QUARTZ
SENSITIVITY
SPECIFICITY
TITANATES
ULTRALOW TEMPERATURE
VERY LOW TEMPERATURE
ZIRCONATES
AROMATICS
CHALCOGENIDES
DATA
ELECTRICITY
ELECTROMAGNETIC RADIATION
ENERGY-LEVEL TRANSITIONS
HYDROCARBONS
HYDROGEN COMPOUNDS
HYDROXIDES
INFORMATION
LASERS
LIQUID LASERS
MINERALS
NEODYMIUM COMPOUNDS
NUMERICAL DATA
ORGANIC COMPOUNDS
OXIDE MINERALS
OXIDES
OXYGEN COMPOUNDS
RADIATIONS
RARE EARTH COMPOUNDS
SILICON COMPOUNDS
SILICON OXIDES
SPECTROSCOPY
TITANIUM COMPOUNDS
TRANSITION ELEMENT COMPOUNDS
ZIRCONIUM COMPOUNDS
400104* - Spectral Procedures- (-1987)