Letter to the Editor

Foreign Gas Broadening Studies of the J' ←J = 1← 0 Rotational Line of CO by Frequency and Time Domain Techniques

“…However the pure gas showed a tendency to negative pressure shift which was estimated to be less than 0.01 MHz/Torr in agreement with a recently reported value within the error limit (-0.027(24) MHz/Torr) [9], Extrapolation to zero pressure yields a center line frequency u 0 = 115 271.202( 1) MHz which is in excellent agreement with the result from sub-Doppler investigations by Winnewisserat al. [16].…”

Analysis of the Line Profiles of CH3CN for theJ= 5 ← 4 andJ= 6 ← 5 Rotational Transitions

“…The reliability of the spectrometer for the present purpose was tested by measuring the absolute intensity and the pressure broadening coefficient of the CO line at 115 GHz (8). The good agreement of our results obtained for CO with the literature values, which have been determined by other methods, guarantees that a spectrometer of the present type can be applied for the present purpose.…”

Absolute Intensity of the NH3 ν2 Band

“…The linear correction term A J , however, is much smaller than expected; the obtained value is very close to that of a nonpolar molecule. This anomaly can be understood by taking into account the tunnel-doubling effect associated with the inversion vibration of NH 3 . In polar molecules, the main part of the linear term can be explained by the intensity borrowing from strong pure-rotational transitions due to the mixing of the wavefunctions by the centrifugal distortion interaction.…”

“…Using a modern FTIR spectrometer of high resolution and high precision, we have tried to determine the line intensities as accurately as possible. The observed line profiles were analyzed by a fit procedure assuming the Voigt-type absorption profile function as described in our previous papers (3)(4)(5)(6).…”