Physical foundations and application of photoacoustic spectroscopy (review)
Photoacoustic spectroscopy (PAS) has been successfully used in studies of the properties of solids. The new nondestructive method measures the part of photon energy that is absorbed by the sample being studied and is transformed into heat. The simple theory of PAS is that an acoustic signal in the photoacoustic chamber is generated owing to the periodical heat flux emitted by the solid into the surrounding gas. Only a relatively thin gas layer near the surface of the solid can thermally follow the periodical heat flux. This boundary gas layer may be considered as an oscillating piston acting on the rest of the gas in the chamber and initiating the acoustical signal. In the case of air, the boundary layer thickness is about 0.2 cm at a modulation frequency of 100 Hz. Some of the examples of PAS cited by the authors in this paper include a study of semiconductors in the case of strong light absorption in the infrared region of the spectrum described. In this case, a PA effect spectrum was observed which consisted of lines with energy level locations corresponding to the light absorption by impurities with deep levels in the forbidden band. The sensitivity of detecting the concentration of such impurities was found to be on the level of 10/sup 13/ atoms/cm/sup 3/.
- Research Organization:
- Technical College, Ilmenau, East Germany
- OSTI ID:
- 6379779
- Journal Information:
- Ind. Lab. (Engl. Transl.); (United States), Vol. 52:3; Other Information: Translated from Zavod. Lab.; 52: No.3, 20-24(Mar 1986)
- Country of Publication:
- United States
- Language:
- English
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36 MATERIALS SCIENCE
PHOTOACOUSTIC SPECTROMETERS
REVIEWS
USES
SEMICONDUCTOR MATERIALS
PHOTOACOUSTIC EFFECT
PHOTOACOUSTIC SPECTROSCOPY
ABSORPTION
AIR
ALUMINIUM
ENERGY LEVELS
EXCITATION
FORBIDDEN TRANSITIONS
INCIDENCE ANGLE
INFRARED RADIATION
OPTICAL PROPERTIES
PHASE SHIFT
PHONONS
PHOTOCONDUCTIVITY
PHOTONS
RADIATIONLESS DECAY
SILVER
SPIN ORIENTATION
THERMAL CONDUCTIVITY
VISIBLE RADIATION
DE-EXCITATION
DOCUMENT TYPES
ELECTRIC CONDUCTIVITY
ELECTRICAL PROPERTIES
ELECTROMAGNETIC RADIATION
ELEMENTARY PARTICLES
ELEMENTS
ENERGY TRANSFER
ENERGY-LEVEL TRANSITIONS
FLUIDS
GASES
INFRARED SPECTROMETERS
MASSLESS PARTICLES
MATERIALS
MEASURING INSTRUMENTS
METALS
ORIENTATION
PHYSICAL PROPERTIES
QUASI PARTICLES
RADIATIONS
SPECTROMETERS
SPECTROSCOPY
THERMODYNAMIC PROPERTIES
TRANSITION ELEMENTS
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