| Budget Amount *help |
¥5,000,000 (Direct Cost: ¥5,000,000)
Fiscal Year 1990: ¥700,000 (Direct Cost: ¥700,000)
Fiscal Year 1989: ¥4,300,000 (Direct Cost: ¥4,300,000)
|
|---|
| Research Abstract |
Recently much interest is directed toward short-lived molecules (ions, free radicals and unstable chemically active molecules), which cannot be synthesized with a usual chemical method. For the observation of the spectrum of such molecules, it is especially important to use a spectrometer of high sensitivity, to produce labile species efficiently and to predict the spectral frequencies as precirely as possible from the estimated structure based on the high-grade quantum chemical calculation of the structure of closely related molecules. In the present study we constructed a microwave spectrometer, which should meet the above conditions and aim to observe the rotational spectrum of the transient species. The characteristic features of the spectrometer are (1) use of a pyrex free-space cell, 2 m in length and 10 cm in diameter, with glow-discharge electrodes in the cell to produce in situ the labile molecule, (2) use of the source modulation by double square waves and observation of the spectrum in the form of the second derivative, (3) stabilization , with a phase-lock loop, of the 10 GHz frequency microwave from a klystron, which is used as the standard of the frequency measurement for the high-frequency millimeter wave and (4) spectrum measurement and data reduction (integration, correction of baseline distortion, determination of the frequencies of the absorption lines, etc.) with the aid of a personal computer. The sensitivity and precision of the spectrometer was tested by observing weak absorption lines of OCS in vibrationally excited states. The lines with the spectral intensity of 1X10^<-8> cm^<-1> could be observed. The measured frequencies agreed well with those calculated from the molecular constants reported in the literature. The spectrum of labile SiCl_2 was observed through the glow discharge of low-pressure SiCl_4. The spectrum of an unknown species was observed in the discharge of HSiCl_3.
|
