ABSTRACT
We present the observation of the N2-H2O van der Waals complex in the 2OH stretch overtone region. The high-resolution jet cooled spectra were measured using a sensitive continuous wave cavity ringdown spectrometer. Several bands were observed and vibrationally assigned in terms of ν1, ν2, and ν3, the vibrational quantum numbers of the isolated H2O molecule, as (ν1'ν2'ν3')â(ν1â³ν2â³ν3â³)=(200)â(000) and (101) â (000). A combination band involving the excitation of the in-plane bending motion of N2 and the (101) vibration of water is also reported. The spectra were analyzed using a set of four asymmetric top rotors, each associated with a nuclear spin isomer. Several local perturbations of the (101) vibrational state were observed. These perturbations were assigned to the presence of the nearby (200) vibrational state and to the combination of (200) with intermolecular modes.
Subject(s)
Water , Water/chemistry , Nitrogen/chemistry , VibrationABSTRACT
Two setups based on CW cavity ring-down spectroscopy were used at Bruxelles and Rennes to record jet-cooled water dimer absorption between 7188 and 7285, and between 7357 and 7386 cm(-1). Some 19 absorption features are reported, significantly more than in the literature. Limited high-resolution information is available due to strong overlap between neighboring vibration-rotation-tunneling (VRT) structures and to spectral broadening induced by short upper state vibrational predissociation lifetimes, likely to range between 100 and 20 ps. Rotational band contours analyses are performed to assign the partly resolved VRT structures to the v1v2v3,vfvb = 000,11; 200,00; 000,20; and 101,00 zero-order vibrational states. Their wavenumbers are found to be 7192.34, 7225.86, 7240.57, and 7256.99 cm(-1), respectively. Both so-called acceptor-switching tunneling components are involved in the assignments whose tentative character is discussed.
ABSTRACT
We have used continuous-wave cavity ring-down and femto-Fourier transform-cavity-enhanced absorption spectrometers to record the spectrum of the OH-stretching + CH-stretching (ν1 + ν2) combination band in trans-formic acid, with origin close to 6507 cm(-1). They, respectively, allowed resolving and simplifying the rotational structure of the band near its origin under jet-cooled conditions (Trot = 10 K) and highlighting the overview of the band under room temperature conditions. The stronger B-type and weaker A-type subbands close to the band origin could be assigned, as well as the main B-type Q branches. The high-resolution analysis was hindered by numerous, severe perturbations. Rotational constants are reported with, however, limited physical meaning. The ν1 + ν2 transition moment is estimated from relative intensities to be 24° away from the principal b-axis of inertia.
ABSTRACT
Cw-CRDS spectra of water-rare gas supersonic expansions were recorded between 7229 and 7262 cm(-1). The effective absorption pathlength was about 1 km in jet-cooled gas and the resolution about 1 × 10(-4) cm(-1). Many well-resolved structures are observed that could be assigned from experimental evidence to H2O-Ar/Kr bands. Eight broader unresolved features are more specifically reported and assigned to small H2O multimers, in good agreement and refining previous observations by Nizkorodov et al. [J. Chem. Phys. 122, 194316 (2005)]. Among these, the band at 7256.5 cm(-1) is shown to be a Q branch of the water dimer with accompanying R and very weak P lines. The band is assigned to a K(a) = 0 â 1 transition and rotationally analyzed, leading to a restricted set of upper state rotational constants. The upper state lifetime (60 ± 3 ps) is extracted from the linewidths.
ABSTRACT
The Π (1(1)) â Σ (0(0)) 2NH (ν1+ν3) band of the NH3-Ar van der Waals complex formed in a supersonic jet expansion, with origin at 6628 cm(-1) was recorded at high-resolution using cavity ring down spectroscopy. The analysis leads to upper state rotational constants and J-dependent predissociation lifetimes estimated from linewidth analysis, with a mean value about 0.6 ns.