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We present a line profile study at 150, 110 and 80 K for the R(7) line in the fundamental band of 13 CO perturbed by Ar in a new stabilized low-temperature cell cooled by liquid nitrogen. The broadening, shifting and narrowing parameters are determined taking into account the absorber speed dependence by simultaneous least-squares fitting of spectra over a 4-300 Torr pressure range recorded using a frequency-stabilized diode laser spectrometer. When the cell is cooled by liquid helium the (1-0) R(2) line of 13 CO in collision with helium is observed at a temperature of 6.9 K. [ABSTRACT FROM AUTHOR]

The vibrational state perturbing the [sup J] = 17 and 18 rotational states of the zero-order ν[sub 1] + 3ν[sub 3] state of [sup 12]C[sub 2]H[sub 2] is assigned to the state with vibrational energy predicted at [sup G[sub v]] = 12685.1cm[sup -1] using the cluster model (EL IDRISSI, M.I., LIÉVIN, J., CAMPARGUE, A. and HERMAN, M., 1999, J. chem. Phys., 110, 2074). The assignment is discussed also in terms of the very special pressure shift behaviour demonstrated previously for absorption lines reaching these levels (HERREGODTS, F., HEPP, M., HURTMANS, D., VANDER AUWERA, J. and HERMAN, M., 1999, J. chem. Phys., 111, 7961). The experimental information arising from a set-up newly running at ULB, called FT-ICLAS brings decisive information in the assignment process. This set-up is described briefly. [ABSTRACT FROM AUTHOR]

A Fourier transform interferometer was used to record the slit-jet cooled absorption spectrum of [sup 12]C[sub 2]H[sub 4] between 700 and 2400cm[sup -1], at a spectral resolution of 0.005 cm[sup -1]. Three bands, υ12 at 1442.442 70(1) cm[sup -1], υ7 + υ8 at 1888.978 23(3) cm[sup -1] and υ6 + υ10 at 2047.775 832(2) cm&-1;, were rotationally analysed. In the case of 7181, a known Coriolis perturbation mechanism involving the nearby 4181 (1958.264 cm-1) and 81101 (1766.391 cm-1) states was accounted for in the analysis. The latter fitting procedure included 12 levels from the 4181 state which are observed because lines from υ4 + υ8 borrow intensity from υ7 + υ8. Compared to the literature, significantly improved vibration-rotation constants were obtained for all upper states reported in the present study. [ABSTRACT FROM AUTHOR]