Spectroscopy Relevant to Astronomical Observations

Observations of interstellar rotational transitions of CH3OH and H2S at 0.8 GHz and 169 GHz, respectively, indicate the wide frequency range now available to radio astronomy. Extension of earthbound observations to 300 GHz can be expected in the near future. The development of sensitive narrow-band IR detectors 

nx is the number of molecules per cm3 in the lower level, ju the electric dipole transition matrix element, Tex the excitation temperature of the molecule and f(y) the line shape function normalized to 

The other quantities have their usual meaning. 

If the number of molecules in the lower state n is expressed in terms of the total number of molecules per cm 3 by means of Eq. (17), 

A comparison may be made between the calculated J - 6—5 transition of CH3CN on the one hand and the interstellar and laboratory spectra on the other shown in Figs. 15 and 16. The latter figure presents the emission lines observed by Solomon et at. in Sgr B2 and the laboratory spectrum of this transition ob- 

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