Line positions and strengths of 16O 12C 18O, 18O 12C 18O and 17O 12C 18O between 2200 and 7000 cm −1

Abstract

Line positions and strengths of 16O 12C 18O (628), 18O 12C 18O (828) and 17O 12C 18O (728) were measured between 2200 and 7000 cm −1 using 22 near infrared (NIR) absorption spectra recorded at 0.01–0.013 cm −1 resolution with the McMath–Pierce Fourier transform spectrometer located at the National Solar Observatory on Kitt Peak, Arizona. These data were obtained at room temperature using absorption cells with optical path lengths ranging from 2.4 to 385 m; the cells were filled with natural and 18O-enriched samples of CO 2 at pressures ranging from 0.54 to 252 torr. The observed line positions were analyzed to obtain the upper state band centers and rotational constants for 17 bands of 16O 12C 18O, 19 bands of 18O 12C 18O and 8 bands of 17O 12C 18O. The majority of the 18O 12C 18O and 17O 12C 18O bands were measured for the first time. In addition, the rotational constants for the lower states 00001, 01101 e and 01101 f were derived for all three species using the method of combination differences in which the averaged values obtained from the line positions of two or more bands were least-squares-fitted. Rovibrational parameters were also obtained for the 02201 e, 02201 f, 10002 and 10001 states of 18O 12C 18O. The line position analysis revealed that transitions of the levels 38 ⩽ J′ ⩽ 46 of the 11111 f ← 01101 f band of 18O 12C 18O are perturbed. Perturbed transitions were also observed for the 12212 ← 02201 band and in the high- J transitions ( J′ ⩾ 49) of the 20012 ← 00001 band of 18O 12C 18O. Band strengths and Herman–Wallis-like F-factor coefficients were determined for 21 bands of 16O 12C 18O, 25 bands of 18O 12C 18O and 8 bands of 17O 12C 18O from least-squares fits to more than 3700 measured transition intensities; band strengths and line positions for 34 of these bands were obtained for the first time.