The collisional broadening of the J '← J = 1 ← 0 rotational line of carbon monoxide by the buffer gases He, Ne, Ar, Kr, CO, N2, O2 , and air has been studied at room temperature. Two different experimental techniques in time- and frequency-domain, respectively, were used. The obtained data are in good agreement. Time-domain investigations on the temperature dependence of the foreign gas broadening parameters are also presented.

$^{g}$H.Maeder, A.Guarnieri, J. Doose N.Nissen, V.N.Markov, A.M stanyuk A.F.Andianov A.F.Krupnov, Jocn Mole Spectr. 180, 183-187(1996) $^{h}$Support by DFG and RFBR grams is gratefully acknowledged

The pressure broadening of the COJ′←J= 1 ← 0 line has been studied by two different techniques. Analysing coherent transients by the time-domain technique yields a broadening parameterCw= 3.43(2) MHz/Torr, whereas the analysis of the absorption spectrum by the frequency-domain technique results inCw= 3.45(3) MHz/Torr.

Rotational and centrifugal distortion constants as well as dipole moments in the three lowest-lying vibrational states of ketene, ν5, ν6, and ν9, have been determined from millimeterwave measurements in the range 40–165 GHz. The rotational constants, in theS-reduction, are (in MHz):A(51) = 311981,A(61) = 289864,A(91) = 228700,B(51) = 10291.373,B(61) = 10284.964,B= 10331.814,C(51) = 9940.304,C(61) = 9934.975,C(91) = 9935.051. Dipole moments are (in D): μgs= 1.42429, μ(51) = 1.37408, μ(61) = 1.40433, μ(91) = 1.42545. The present measurements and our previous data on ketene-d2[J. Dooseet al., Z. Naturforsch. A44,538 (1989)] have been compared to recentab initioresults [A. L. L. East,J. Chem. Phys.102,8506 (1995)]. The agreement between experimental and theoretical vibration–rotation interaction constants is generally good with some notable exceptions, especially for ketene-d2.

Details are presented of a spectrometer which allows the recording of molecular emission signals in the frequency region of 100 GHz with subsequent Fourier transformation. Results are given of first experiments, which use the described technique for investigating the pressure broadening of the J' <-- J: 7 <-- 6 transition of carbonyl sulphide (OCS) and the temperature dependence of the pressure broadened linewidth of the J' <-- J : 1 <-- 0 rotational transition of carbon monoxide (CO).

We present the details of a new type of spectrometer which allows the recording of molecular emission signals in the microwave and millimeter wave region with subsequent Fourier transformation. First experiments up to 49 GHz have been carried out, but we claim that the biphase modulator used to 49 GHz will allow broadbanded spectroscopy up to the 100-GHz region.

Abstract The boron and nitrogen hyperfine structure in the rotational spectra of two aminoborane isotopomers, 11 BH2NH2 and 10BH2NH2, has been investigated and the quadrupole coupling constants of boron 10B, 11B and nitrogen 14N have been determined. We get the following results for the nuclear quadrupole coupling constants: χaa(11B) = -1.684 (14) MHz, χbb(11B) = -2.212 (11) MHz, χcc(11B) = 3.896(11) MHz, χaa(10B) = -3.481 (11) MHz, χbb(10B) = -4.623 (14) MHz, χCC(10B) = 8.104 (14) MHz and xaa(14N) = 0.095 (9) MHz, χbb(14N) = 2.091 (8) MHz, χcf4 (14N)=-2.186 (8) MHz. These nitrogen quadrupole coupling constants are those of the 11BH2 NH2 isotopomer. Additionally we were able to determine two out of the three spin rotation coupling constants caa, cbb, and ccc of boron, caa(11 B = 55.2 (26) kHz, cbb(11B) = 6.62 (36) kHz, caa (10B) = 15.26 (69) kHz and cbb(10B) = 4.94 (70) kHz. The spin rotation coupling constants ccc had to be fixed to zero in both cases. Furthermore we measured the rotational spectra in the mm-wave region to determine all quartic and several sextic centrifugal distortion constants according to Watson's A and S reduction

D2CCO has been investigated in the first excited vibrational states of the ν9, ν6, and ν5 vibrations. About 150 transitions have been measured partly at room temperature and partly at 360 K using a micro- and millimeter-wave spectrometer provided with an averaging system using a personal computer. Rotational and centrifugal distortion constants have been obtained for the excited states mentioned. A simultaneous least squares analysis of these MW-data with upper state combination differences obtained from FT-IR data has been carried out. Improved sets of molecular parameters have been obtained.

Several K = 3 doublets of 14ND3 and 15ND3 in the ν2 = 1 excited vibrational state have been observed. With the new lines we were able to obtain improved values for the η3 0 and η3 J constants. For 14ND3 η3 0 = 2.3517(15) · 10-5 MHz, η3 J= -1.068(8) ·10-8 MHz, and for 15ND3 η3 0 = 2.3548(23) · 10-5 MHz, η3 J = 1.061(10)· 10-8 MHz.