Excess ultrasonic absorption in H2O-D2O mixture

The two state model of Hall (1948) and new relations for the relaxation time and structural compressibility were used to calculate the ultrasonic absorption in excess of the classical values of H₂OD₂O mixture at 30°C. There is good agreement between the calculated and experimental values of excess absorption. The molar free energy difference and the molar volume change calculated for the open-packed and close-packed states agree well with the values reported by Kor et al. (1972).     

Spectroscopically determined potential energy surfaces of the H2O, H2O, and H2O isotopologues of water

Adiabatic potential energy surfaces (PESs) for three major isotopologues of water, H₂¹⁶O, H₂¹⁷O, and H₂¹⁸O, are constructed by fitting to observed vibration-rotation energy levels of the system using the nuclear motion program DVR3D employing an exact kinetic energy operator. Extensive tests show that the mass-dependent ab initio surfaces due to Polyansky et al. [O.L. Polyansky, A.G. Császár, S.V. Shirin, N.F. Zobov, P. Barletta, J. Tennyson, D.W. Schwenke, P.J. Knowles, Science 299 (2003) 539-542.] provide an excellent starting point for the fits. The refinements are performed using a mass-independent morphing function, which smoothly distorts the original adiabatic ab initio PESs. The best overall fit is based on 1788 experimental energy levels with the rotational quantum number J = 0, 2, and 5. It reproduces these levels with a standard deviation of 0.079 cm⁻¹ and gives, when explicit allowance is made for nonadiabatic rotational effects, excellent predictions for levels up to J = 40. Theoretical linelists for all three isotopologues of water involved in the PES construction were calculated up to 26 000 cm⁻¹ with energy levels up to J = 10. These linelists should make an excellent starting point for spectroscopic modelling and analysis.     

Wavelength-agile H2O absorption spectrometer for thermometry of general combustion gases

Using a novel Fourier-domain mode-locking (FDML) laser scanning 1330-1380 nm, we have developed a gas thermometer based on absorption spectroscopy that is appropriate for combustion gases at essentially arbitrary conditions. The path-integrated measurements are particularly useful in homogeneous environments, and here we present measurements in a controlled piston engine and a shock tube. Engine measurements demonstrate a RMS temperature precision of ±3% at 1500 K and 200 kHz bandwidth; the precision is improved dramatically by averaging. Initial shock tube measurements place the absolute accuracy of the thermometer within ∼2% to 1000 K. The sensor performs best when significant H₂O vapor is present, but requires only at 300 K, at 1000 K, or at 3000 K for 2% accurate thermometry, assuming a 4 kHz measurement bandwidth (200 kHz scans with 50 averages). The sensor also provides H₂O mole fraction and shows potential for monitoring gas pressure based on the broadening of spectral features. To aid in designing other sensors based on high-temperature, high-pressure H₂O absorption spectroscopy, a database of measured spectra is included.     

Far-infrared absorption intensities of H2O and D2O in C6H6

Far-i.r. absorption intensities have been measured for H₂O and D₂O in C₆H₆ solutions. Beer's law plots were found to be nonlinear. From the plots, the equilibrium constants of dimer formation in benzene were estimated to be 2.4M^-1 and 3.3M^-1 for H₂O and D₂O at 20°C, respectively. Based on Onsager's reaction field and including explicitly the effect of differences in molecular size between solute and solvent molecules, the internal moment of a water molecule and the volume ratio of a molecule to a cavity were estimated from the integrated absorption intensity of a D₂O monomer in C₆H₆ as 1.98 D and 0.7, respectively     

Fourier transform absorption spectra of H2O and H2O in the 8000-9400 cm spectral region

Fourier transform spectra of water vapor enriched in ¹⁸O and ¹⁷O were recorded between 8012 and 9336 cm⁻¹ and analyzed for the first time. High accuracy ab initio predictions of line positions and intensities by Partridge and Schwenke [J. Chem. Phys. 106 (1997) 4618-4639; 113 (2000) 6592-6597] were used in the process of spectrum assignment. Transitions involving the (031), (111), (130), (210), and (012) upper vibrational states were identified in the recorded spectra. As a result, 514 and 244 precise ro-vibrational energy levels were derived for the H₂¹⁸O and H₂¹⁷O molecules, respectively. High-order resonance perturbations between levels of the vibrational states involved were evidenced leading to the identification of a number of rotational levels of the (050) and (060) highly excited bending states.     

Collisional broadening and shifting of the 211-202 transition of H2O, H2O, H2O by atmosphere gases

Broadening and shifting of the 2₁₁-2₀₂ transition of H₂¹⁶O, H₂¹⁷O, H₂¹⁸O by pressure of water, nitrogen and oxygen were precisely measured at room temperature using spectrometer with radio-acoustic detection of absorption. Shift parameters for all studied lines as well as broadening parameters of H₂¹⁷O, H₂¹⁸O lines were measured for the first time. Comparison of obtained results with previously known experimental and theoretical data is presented.     

Penning ionization electron spectroscopy of H2O,D2O,H2S and SO2

Electron energy peak shifts and peak shapes were determined in the ionization of H₂O, D₂O, H₂S and SO₂ by Ne(³P₂) and He(2¹S, 2³S) metastable atoms. The shifts are large, especially in ionization of H₂O and D₂O into the ionic ground state and are probably mostly due to chemical interaction during the collision.In a previous paper the electron energy distribution curves for ionization of CO, HCl, HBr, N₂O, NO₂, CO₂, COS and CS₂ by helium, neon and argon metastables and the characteristics of this ionization were described¹. In this paper the series of triatomic molecules was extended to the molecules H₂O, D₂O, H₂S and SO₂. Because all these molecules have considerable dipole moments it could be expected that the peak shifts might be enhanced as compared with other triatomic molecules.     

Fourier-transform absorption spectroscopy of H2O in the first hexade region

The Fourier-transform absorption spectrum of H₂¹⁸O was recorded in the 6000-7940 cm⁻¹ region and assigned on the base of the very accurate ab initio calculations by Partridge and Schwenke (PS) [J. Chem. Phys. 106 (1997) 4618-4639; J. Chem. Phys. 113 (2000) 6592-6597]. A set of 821 accurate rovibrational energy levels was obtained for six interacting states of the first hexad: (101), (120), (021), (200), (002), and (040). 290 of them are reported for the first time. The experimental line intensities are also estimated and compared with the PS calculations and the available literature data in the considered spectral range.     

Infrared absorption intensities for N2O

The infrared strengths of the three fundamental absorption bands and 10 overtone and combination bands of nitrous oxide, N₂O, were measured with a Fourier transform spectrometer.     

INS investigation on disaccharide/H2O mixtures

New Inelastic Neutron Scattering findings on homologues disaccharides (C₁₂H₂₂O₁₁)/H₂O mixtures are presented. The comparison among the spectra of trehalose, maltose and sucrose/H₂O mixtures, besides evidencing a different destructuring effectiveness on the H₂O hydrogen bond network, and hence different cryoprotectant properties, shows a higher ‘crystallinity’ degree for the trehalose/H₂O system which accounts for its higher ‘rigidity’. This result justifies the better cryptobiotic action of trehalose in respect to maltose and sucrose.     

Line-by-line and narrow-band statistical model calculations for H2O

In line-by-line calculations we use hot-band lines generated from the AFGL or GEISA data. The parameters of a random statistical model are calculated from these lines for 25 cm^-1 wide intervals. Comparisons are made between experimental spectra and results of the two theoretical models for the 1595 and 3755 cm^-1 bands between 900 and 1500 K. The validities of the statistical model and of the Curtis-Godson and Lindquist-Simmons approximations for nonisothermal and inhomogeneous media are tested.     

Vibronic transition moments and line intensities for H2O

Ab initio calculations of the electronic dipole moment components for the and electronic states and the electronic transition moment for the - transition of H₂O⁺ have been carried out. Parameterized analytical functions have been fitted through the computed ab initio data points, and the resulting dipole moment and transition moment surfaces have been used, along with potential energy surfaces derived from the ab initio results of Brommer et al. [J. Chem. Phys. 98 (1993) 5222], to simulate H₂O⁺ spectra and to generate an extensive set of vibronic transition moments for the and band systems of H₂O⁺. The work is made with the dual purpose of facilitating further assignments of high-resolution spectra [J. Mol. Spectrosc. 219 (2003) 258] and of allowing cometary spectra of H₂O⁺ to be simulated [Ap. J. 574 (2002) L183].     

Fourier transform absorption spectra of H2O and H2O in the 3ν + δ and 4ν polyad region

Fourier transform absorption spectra of H₂¹⁸O-enriched and H₂¹⁷O-enriched water vapor in the 3ν + δ and 4ν polyad region have been analyzed. With the aid of theoretically calculated linelists, we have assigned 1014 lines attributed to H₂¹⁸O and 836 lines of 855 attributed to H₂¹⁷O. Seven new band origins are found for H₂¹⁷O and one for H₂¹⁸O.     

Magnetic phase diagram of MnBr24H2O

The magnetic phase diagram of the monoclinic antiferromagnet MnBr₂4H₂O (obtained from differential magnetization measurements) is presented for temperatures down to T = 0.3 K, and for applied magnetic fields parallel to the crystallographic axes a', b and c. For H∥c an unusual behaviour is observed below T ≈ 0.55 K where the antiferro-paramagnetic boundary apparently splits into three others. It is shown that our critical fields extrapolated to T = 0 are consistent with a recent theory proposed by Becerra and Ferreira.     

Absolute photoabsorption cross sections for H2O and D2O from λ 180–790 Å

Absolute photoabsorption cross sections for H₂O and D₂O have been measured photoelectrically from λλ 180 to 790 Å using synchrotron radiation. The cross sections increase smoothly with wavelength to ～λ610 Å, with both H₂O and D₂O displaying a broad absorption band extending above a nearly linear background from λλ 400 to 490 Å. The continuum has a maximum of ～ 22.5 Mb at λ 640 Å. Above λ 615 Å, superimposed on the continuum, a diffuse structure appears which is similar to the vibrational structure of the ²B₂ states of H₂O⁺ and D₂O⁺ as observed in photoelectron spectra. The structure is believed to arise from excitation of a 1b₂ electron to the vibrational levels of a Rydberg orbital with n¹ ≈ 2.64.     

Phase transitions in RbCoCl3 · 2H2O

Differential susceptibility measurements were performed on a single crystal of RbCoCl₃ · 2H₂O. An anti-ferromagnetic ordering was found at 2.975 K.     

Scattered-wave calculations of photoionization cross-sections and asymmetry parameters for CO,H2O and H2S

Partial photoionization cross-sections and asymmetry parameters are calculated for the valence orbitals of the molecules CO, H₂O, and H₂S and of the atoms O and S using a recently developed extension of the self-cosistent field— Xα—scattered-wave method to continuum states. The convergence of the partial-wave expansions for both initial and final states is studied for electron kinetic energies in the range 2–1000 eV. Since convergence is very slow at high kinetic energies, the interesting region between 2 and 50 eV is emphasized, and comparisons are made with experimental UV photoemission results where such data are available. Overall the method appears to be far more reliable than previous calculations for polyatomic molecules which have used plane-wave or orthogonalized plane-wave final states.