Direct observation of transient fluorine atoms with 25-µm wavelength-stabilized diode laser absorption
| Autor: | Gary W. Loge, Herbert A. Fry, Norris G. Nereson |
|---|---|
| Rok vydání: | 2010 |
| Předmět: |
Tunable diode laser absorption spectroscopy
Materials science Absorption spectroscopy Excimer laser business.industry Materials Science (miscellaneous) medicine.medical_treatment Absorption cross section Physics::Optics Laser Fluence Industrial and Manufacturing Engineering law.invention Optics law Ultrafast laser spectroscopy medicine Physics::Atomic Physics Business and International Management Atomic physics Spectroscopy business |
| Zdroj: | Applied optics. 33(15) |
| ISSN: | 1559-128X |
| Popis: | Through the use of continuous diode laser absorption, detection of transient fluorine atoms with an initial number density in the range of 10(14) cm(-3) has been demonstrated. A crucial part of the continuous-detection technique was laser frequency stabilization with a reference cell of atomic fluorine with Zeeman modulation of the absorption lines to generate a feedback signal. Long-term wavelength stability was demonstrated with second-harmonic phase-sensitive detection of the second-derivative signal for periods up to several hours. For determination of the short-term wavelength stability in the range of microseconds to seconds, a transient signal was generated by photolysis of F(2) with an excimer laser at 308 nm. The initial diode laser absorption was compared to a calculated value obtained from the measured excimer laser fluence, the known dissociation cross section of F(2), and the atomic fluorine absorption cross section, which included a statistical population distribution, the finite bandwidth of the laser dode, and the effects of pressure broadening. The observed absorption was approximately 33% less than the calculated value, possibly because of the diode laser's wavelength instability on the time scale of a few seconds, which is consistent with an observed amplitude instability from pulse to pulse when pulsed at 1-10 Hz. |
| Databáze: | OpenAIRE |
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