Two-step laser excitation and field-ionization of krypton and xenon atoms in collinear fast-beam laser spectroscopy /
In the context of ultra-trace detection and spectroscopy of trace amounts of the noble gases krypton and xenon, a collinear fast-beam laser-spectroscopy method was developed. In both fundamental research of short-lived isotopes, as well as in practical applications the task lies in devising a method...
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| Format: | Thesis Book |
| Language: | English |
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[Place of publication not identified] :
[publisher not identified] ;
2000.
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| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=727726291&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | In the context of ultra-trace detection and spectroscopy of trace amounts of the noble gases krypton and xenon, a collinear fast-beam laser-spectroscopy method was developed. In both fundamental research of short-lived isotopes, as well as in practical applications the task lies in devising a method that efficiently uses the minute sample sizes (in general less than 1013 atoms) with a trace isotope content below 1 part in 10¹⁰. This requires both an efficient and highly isotope-selective sample preparation and detection method. A promising technique for the noble gases, in this context, is two-step resonant excitation from the efficiently populated metastable state into a Rydberg state with subsequent field ionization and particle detection in collinear fast beam laser spectroscopy. We have performed this experiment for Kr and Xe atoms. It was shown that the required isotope selectivity can be achieved by using two-step laser excitation into a Rydberg state and subsequent field-ionization with particle detection. The fast-beam technique enhances the isotope selectivity by introducing large artificial isotope shifts. The sensitivity is also inherently large, as velocity bunching allows for efficient laser excitation of all atoms in the beam. The spectroscopically accessible metastable states of the noble gases can be efficiently populated by resonant charge-exchange. Field-ionization is done state selectively for further background signal reduction. The produced ions are detected on a channeltron. The overall selectivity is determined by the individual selectivities of the laser excitation steps, the selectivity of the field-ionization, and the energy analysis of the signal-ions. It was shown that with continuous wave lasers, one of which is at a fixed frequency, the Xe 13s, 14s and 15s, as well as the Kr 10s, 29d, and 31s Rydberg states were efficiently populated, and subsequently ionized by collisional and/or field-ionization. The critical field strengths for field-ionization were determined. This opens the door for further systematic spectroscopic studies of other noble gas Rydberg atoms, as well as trace-detection of their rare isotopes. |
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| Item Description: | Vita. "Major Subject: Physics". |
| Physical Description: | xii, 135 leaves : illustrations ; 28 cm. Issued also on microfiche from University Microfilm Inc. |
| Bibliography: | Includes bibliographical references (leaves 119-130). |