RESUMEN
A laser photoacoustic technique has been used to measure the absorption spectrum of HCN in the region from 11 390 to 13 020 cm(-1) with a resolution that is limited by the Doppler- and pressure-broadened linewidth. This is a very sensitive technique that has allowed us to measure very weak bands with a small volume of gas. These measurements provide the rovibrational constants for a number of newly observed vibrational energy levels. Copyright 2000 Academic Press.
RESUMEN
A spectrum of HSiF(3) has been recorded at room temperature with a gas pressure of 20-50 Torr in the near-infrared region. A laser photoacoustic spectrometer consisting of a longitudinal resonant cell coupled to a titanium:sapphire ring laser was employed. The 5nu(1) and 6nu(1) overtone bands of H(28)SiF(3) associated with the Si-H stretching have been observed at high resolution (3 x 10(-2) cm(-1)) in the regions 10 900-10 960 and 12 875-12 925 cm(-1), respectively. About 450 lines of the 5nu(1)-0 band have been assigned (J
RESUMEN
The effective operator approach is applied to the calculation of both line positions and line intensities of the (13)C(16)O(2) molecule. About 11 000 observed line positions of (13)C(16)O(2) selected from the literature have been used to derive 84 parameters of a reduced effective Hamiltonian globally describing all known vibrational-rotational energy levels in the ground electronic state. The standard deviation of the fit is 0.0015 cm(-1). The eigenfunctions of this effective Hamiltonian have then been used in fittings of parameters of an effective dipole-moment operator to more than 600 observed line intensities of the cold and hot bands covering the nu(2) and 3nu(2) regions. The standard deviations of the fits are 3.2 and 12.0% for these regions, respectively. The quality of the fittings and the extrapolation properties of the fitted parameters are discussed. A comparison of calculated line parameters with those provided by the HITRAN database is given. Finally, the first observations of the 2nu(1) + 5nu(3) and nu(1) + 2nu(2) + 5nu(3) absorption bands by means of photoacoustic spectroscopy (PAS) is presented. The deviations of predicted line positions from observed ones is found to be less than 0.1 cm(-1), and most of them lie within the experimental accuracy (0.007 cm(-1)) once the observed line positions are included in the global fit. Copyright 2000 Academic Press.
RESUMEN
The laser absorption spectroscopy of molecular ions using the velocity-modulation technique has been employed in the UV region. The absorption source was a cw single-mode laser beam from an extra-cavity frequency doubling unit associated with a dye laser. The high-resolution spectrum of the First Negative system B(2)Sigma(+)(u)-X(2)Sigma(+)(g) of N(+)(2) has been studied. The N(+)(2) ions were produced with an electric discharge in a flowing gas mixture of He/N(2). Seven vibrational bands of the Deltav = 2 sequence (v' = 2-8) have been observed in the region between 30 000 and 30 600 cm(-1), and five of them for the first time at high resolution (v' = 2-4, 6, 7). A set of 770 lines have been assigned; among them are several extra - lines belonging to the A(2)Pi(u)-X(2)Sigma(+)(g) system. A standard model has been used to consider the perturbations between the rovibrational levels of the B(2)Sigma(+)(u) and A(2)Pi(u) states. An improved set of deperturbed constants and effective interaction parameters were derived for the v(B) = 3-v(A) = 14 and v(B) = 7-v(A) = 20 complexes. Copyright 1999 Academic Press.
RESUMEN
A spectrum of natural OCS has been recorded in the near-infrared region using the laser photoacoustic technique. The source is a titanium-sapphire laser pumped by an Ar(+) laser. The tunable 1.5 W beam was sent through the photoacoustic cell. This windowless longitudinal resonant cell was designed with two lambda/4 buffer volumes at both ends in order to reduce the noise and so to increase the sensitivity (alpha(min) approximately 10(-9) cm(-1)). The spectrum of OCS, at a pressure of 90 Torr, has been recorded in the regions 11 953-12 084, 12 829-12 890, and 12 998-13 001 cm(-1). In addition to the 00(0)6-00(0)0 band of (16)O(12)C(32)S recently identified by Ch. Hornberger, B. Boor, R. Stuber, W. Demtröder, S. Naïm, and A. Fayt, J. Mol. Spectrosc. 179, 237-245, 1996, new weaker bands have been observed: 04(0)5-00(0)0, 1 10(0)3-00(0)0, 10(0)6-00(0)0, 14(0)5-00(0)0, 02(0)6-00(0)0, and 01(1)6-01(1)0, and also the 00(0)6-00(0)0 band of (16)O(12)C(34)S. Effective state parameters are deduced from the band-by-band least-squares fits. The new data have also been introduced in the global analysis which takes into account the l-type resonance and the main anharmonic interactions and so allows a full understanding of the perturbations and the intensity transfers. Copyright 1999 Academic Press.
RESUMEN
The Ã2A1-&Xtilde;2B1 electronic transition of NH2 is reinvestigated in the region of its barrier to linearity. A detailed rotational analysis is performed on its laser optogalvanic spectrum recorded in the region 11 300-14 300 cm-1 and on its near infrared Fourier transform emission spectrum. Many new excited levels are identified resulting from more than 2900 assigned lines. A number of them are high levels of &Xtilde;2B1. A set of molecular parameters has been obtained. Numerous perturbations are detected and discussed. This analysis confirms the predictions obtained from previous calculations and allows the estimation of their accuracy. Copyright 1999 Academic Press.
RESUMEN
The molecular ion TiF+ has been observed for the first time using high-resolution spectroscopy. The ions were produced in the positive column of an AC glow discharge with a gas mixture of He/TiF4. A single-mode cw dye laser along with the velocity modulation detection technique was used to record an absorption spectrum in the spectral region 16 800-18 600 cm-1. The observed system was assigned to the 0-0 and 1-1 bands of the [17.6]3Delta-X3Phi transition of TiF+. The rotational analysis of the main subbands has been performed up to J values equal to 77 and 56 for the 0-0 and 1-1 bands, respectively. Despite a careful search, no intercombination band was observed. A set of effective molecular parameters has been determined, characterizing the v = 0, 1 levels of the [17.6]3Delta and X3Phi states. The spin-orbit constants Ae and the vibrational constants omegae, omegaexe have been estimated for both electronic states, as well as their equilibrium distances Re (1.7509 and 1.7800) Å for the [17.6]3Delta and X3Phi states, respectively). Copyright 1998 Academic Press.