Spectroscopy of supercooled gases
A method of obtaining molecular spectra of molecules in the gaseous state at a temperature near absolute zero is described. The method is called supersonic free-jet spectroscopy. This allows spectra that are normally too complex to be interpreted to be simplified so that interpretation and understanding becomes possible. Cooling of the molecule without condensation is accomplished by mixing the vapor of the substance with a carrier gas, usually He, and expanding it through a nozzle usually 0.05 mm ID into a vacuum chamber. Molecular cooling to within a fraction of a degree of absolute zero occurs. A frequency-tunable laser beam transverses the expanding gas cloud at right angles to the direction of flow from the jet 10 to 12 mm from the nozzle. Molecules excited by the laser beam are detected by fluorescence or absorption of the laser beam at a given frequency. It is also possible to produce ionized molecules using a second laser beam and detect them. A range of molecular sizes from He to complex organic molecules may be studied. The temperature at which the molecules are studied may be varied by varying the pressure in the vacuum chamber and the size of the orifice.
- OSTI ID:
- 5622353
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
400104 -- Spectral Procedures-- (-1987)
400500* -- Photochemistry
ABSOLUTE ZERO TEMPERATURE
ABSORPTION SPECTROSCOPY
ELECTROMAGNETIC RADIATION
EMISSION SPECTROSCOPY
FLUIDS
FLUORESCENCE SPECTROSCOPY
GASES
LASER RADIATION
MOLECULAR STRUCTURE
RADIATIONS
SPECTROSCOPY