A Broadband Submillimeter Wave Spectrometer System with On‐Line Microcomputer Data Analysis

Abstract

E. Schafer and M. Winnewisser: A Broadband Submillimeter Wave Spectrometer System etc. 327 higher alcohols approach the "normal" value of k , = 18 J h o l has been explained by a decreasing degree of association [ 161.From the theorem of corresponding states [15,16] one would expect equal values of surface tension at equal relative distances from the critical point. We have calculated the surface tension at half the critical temperature for each alcohol (last row in Table 3). Within +2% a surface tension of 25 mN/m is found for all alcohols investigated.to critical temperatures is obeyed for a variety of liquids. Considering the homologous trend of the boiling points (Fig. 3) the value of rS, = 313.5 " C for n-hexanol (Ref.[12]) appears to be too low. No value for LS, exists for n-pentanol.E 5344 1970.Berlin 1957. Absorptionsspektren, Mikroweilen / Apparate und Methoden / GaseA submillimeter wave spectrometer operating in the frequency range 100 to 800 GHz has been constructed for the study of transient molecules in the gas phase. The instrument employs harmonic generation of millimeter wave frequencies and a He-cooled lnSb photoconducting detector. A high degree of flexibility is achieved using an exchangeable free-space Pyrex absorption cell and a microcomputer for on-line data analysis. The spectrometer can be operated in a free-running video mode together with a fast signal averager or phase-locked to a microwave reference with source modulation. It is shown that the reproducibility of line center frequency measurements up to 600 GHz is i. 10 kHz. Transitions with absorption coefficients of at least 3 . lo.-* cm-' can be detected in the range from 150 to 250 GHz. Ground state rotational transitions of OCS between 200 and 690 GHz are reported and analysed together with previous data.

Line shape of amplitude or frequency-modulated spectral profiles including resonator distortions

“…While the quest for high precision concerns all spectral ranges from radiofrequency [9] to microwave and submillimeter wave spectroscopy toward XUV spectroscopy [10][11][12][13][14], microwave and gigahertz spectroscopy in the millimeter and submillimeter range has been traditionally a field of very high precision. High-precision analyses of gigahertz spectra have been discussed repeatedly for some decades, proposing a variety of techniques often in conjunction with the prototype molecules carbon monoxide (CO), carbon oxide sulfide (OCS), and others [15][16][17][18][19][20]. However, reviewing the current status of precise determinations of line shapes and positions in gigahertz spectroscopy, it seems that there remains considerable room for improvement.…”