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.     

High resolution pure rotational spectrum of water vapor enriched by H217O and H218O

The pure rotational spectrum of a mixture of H₂¹⁶O, H₂¹⁷O and H₂¹⁸O between 50 and 730 cm^?1 was recorded on the Fourier transform spectrometer at the University of Oulu. The resolution achieved was about 0.010 cm^?1 and the precision of the unblended lines was better than 0.001 cm^?1. About 1100 lines were assigned. The measured line positions of H₂¹⁷O and H₂¹⁸O were compared with the values derived from the rotation and distortion constants given in the literature.     

EPR studies of Gd3+-doped Ce2(SO4)3.8H2O and La2(SO4)3.9H2O single crystals

EPR spectra of Gd³⁺-doped Ce₂(SO₄)₃.8H₂O and La₂(SO₄)₃.9H₂O single crystals have been measured with an X-band spectrometer at room and low temperatures. The absolute signs of spin Hamiltonian parameters have been determined for the La₂(SO₄)₃.9H₂O host from intensities of lines at liquid helium temperature; for the Ce₂(SO₄).8H₂O host the lines broaden considerably below 60 K, not permitting the determination of absolute signs of spin Hamiltonian parameters. The data are analysed using a rigourous least-squares procedure, fitting simultaneously all lines obtained for several orientations of the external magnetic field. The zero-field splittings have been computed for both the hosts. The characteristics of EPR spectra of Gd³⁺ in these hosts are compared with those obtained in other rare-earth trisulphate octahydrate hosts.     

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.     

Absorption Spectrum of H2O in the Range 12 400-14 520 cm

Fourier transform spectra recorded using (a) natural abundance water vapor, (b) H₂¹⁸O-enriched water vapor, and (c) H₂¹⁷O-enriched water vapor are analyzed. The ratio of intensities in three spectra is used to identify 927 lines due to absorption by H₂¹⁸O. Intensities and self-broadening parameters are derived for these lines. Using theoretical linelists, comparisons with previously assigned H₂¹⁶O spectra, and automatic searches for combination differences, 747 lines are assigned. These lines belong to 14 vibrational states in the 3ν+δ and 4ν polyads. Newly determined H₂¹⁸O vibrational band origins include 4ν₁ at 13 793.09 cm⁻¹, 3ν₁+ν₃ at 13 795.40 cm⁻¹, 2ν₁+2ν₃ at 14 188.82 cm⁻¹, ν₁+3ν₃ at 14 276.34 cm⁻¹, and 2ν₂+2ν₂+ν₃ at 13 612.71 cm⁻¹. These results are compared with data in HITRAN.     

Line positions and intensities for the ν1 + ν2 and ν2 + ν3 bands of H2O

The intensities of about 90 lines of the ν₁ + ν₂ and ν₂ + ν₃ bands of H₂¹⁸O have been measured using a Fourier transform spectrum of natural water vapor. The constants involved in the rotational expansion of the transformed transition moment operators corresponding to these bands have been determined through a fit of these line intensities. The constants obtained are used to compute the whole spectrum of the ν₁ + ν₂ and ν₂ + ν₃ bands of H₂¹⁸O providing reliable line positions and intensities. For lines involving perturbed levels a comparison is given with the results obtained for H₂¹⁶O and it is shown that the results for one isotopic species cannot be transferred directly to another one.     

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.     

Centrifugal distortion analysis of pure rotational spectra of H216O,H217O,and H218O

Centrifugal distortion analyses based entirely on high-quality infrared data are carried out for the ground vibrational states of H₂¹⁶O, H₂¹⁷O, and H₂¹⁸O. As a result of the analyses, the values of 27 rotation and distortion constants for each species are determined. By using these constants it was possible to improve considerably the accuracy of the literature values for rotational energy levels at high J_τ, especially for H₂¹⁷O and H₂¹⁸O. The experimental values for the energy levels are deduced from the observed rotational transitions constituting the fitted data.     

A spectroscopic study of water vapor isotopologues H2O, H2O and HDO using a continuous wave DFB quantum cascade laser in the 6.7 μm region for atmospheric applications

A quantum cascade spectrometer was used in the laboratory to study H₂¹⁶O, H₂¹⁸O and HDO line intensities near 6.7 μm. The spectral region ranging from 1483 to 1487 cm⁻¹, which is suitable for the in situ laser sensing of these isotopologues in the atmosphere, was investigated using a continuous-wave distributed feed-back quantum cascade laser. Eight lines of water vapor isopologues were studied—one line of the ν₂ band of H₂¹⁶O, one line of the 2ν₂-ν₂ band of H₂¹⁶O, two lines of the ν₂ band of H₂¹⁸O and four lines of the ν₂ band of HDO were carefully revisited. The measured intensities were thoroughly compared to relevant molecular databases and other experimental and calculated results. We also observe that the H₂O, D₂O, HDO equilibrium constant agrees excellently with previously determined values.     

A precise study of the rotational spectrum of formaldehyde H2CO, H2CO, H2CO, H2CO

The rotational spectra of formaldehyde, H₂¹²C¹⁶O and its isotopic species H₂¹³C¹⁶O, H₂¹²C¹⁸O, and H₂¹³C¹⁸O have been investigated in the ground vibrational state in the frequency region between 8 and 460 GHz. For most cases in which measurements of the a-type R- and Q-branch transitions already existed the accuracy of the line position has been improved to about 10 kHz. For H₂¹²C¹⁶O and H₂¹³C¹⁶O a large number of ΔK_a = ±2 transitions were measured with similar accuracy. These new data when combined with all other available data and appropriate weightings lead to a set of ground state parameters which for the first time are compatible with infrared and ultraviolet data. The rotational constants (and 3σ standard deviations) obtained using Watson's A-reduced Hamiltonian are:

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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.     

Electron impact ionization of Ar n , (H2O) n , Ar n (H2O) m clusters

Signals from ions forming in a supersonic molecular beam consisting of an argon-water vapor mixture are measured as functions of the exciting electron energy in the range to 120 eV. The thresholds of electron impact excitation of (H₂O) _{n − 1}H⁺ and Ar _n (H₂O _m ⁺ clusters are determined for the first time. It is found that the proton-hydroxyl group binding energy decreases considerably both in the case of water molecule clustering and when mixed Ar _n (H₂O) _m clusters arise.     

Study of the luminescence of H2O and D2O ices induced by charged-particle bombardment

We measured the optical emission of H₂O and D₂O ices in visible region (300-500 nm) induced by energetic hydrogen ions (H⁺, H₂⁺, and H₃⁺) irradiation. Our analysis of the data of ion-stimulated luminescence (ISL) shows that all spectra of ISL emission are identical, independent of projectile. We show that all lines in the ISL emission spectrum may be assigned to decays from excited particles and/or fragments of H, H₂, OH, and H₂O. From the independence of emission spectrum on projectile we conclude that the final process causing the emissions may be attributed to the interaction between H⁺ (and/or H) and the water molecules.     

High sensitivity ICLAS of H2O in the 12,580-13,550 cm transparency window

High-sensitivity Intracavity Laser Absorption Spectroscopy (ICLAS) is used to measure the high resolution absorption spectrum of H₂¹⁸O between 12,580 and 13,550 cm⁻¹. This spectral region covers the 3v+δ polyad of very weak absorption. Four isotopologues of water (H₂¹⁸O, H₂¹⁶O, H₂¹⁷O, HD¹⁸O) are found to contribute to the observed spectrum. Spectrum analysis is performed with the aid of variational calculations and allowed for assigning 1126 lines belonging to H₂¹⁸O, while only 160 H₂¹⁸O lines are included in the HITRAN-2008 database. Altogether, 823 accurate energy levels of H₂¹⁸O are determined from transitions attributed to 26 upper vibrational states, 438 of them being reported for the first time. New information includes energy levels of four newly observed vibrational states of H₂¹⁸O: (2 4 0), (1 4 1), (0 4 2) and (2 3 1) at 13,167.718, 13,212.678, 13,403.71 and 15,073.975 cm⁻¹, respectively. H₂¹⁸O transitions involving highly excited bending states like (1 6 0), (0 6 1), (0 7 1), (1 7 0), (0 9 0) and even (0 10 0) have been identified as a result of an intensity borrowing from stronger bands via high-order resonance interactions. Thirty-six new energy levels of H₂¹⁷O, present with a 2% relative concentration in our sample, could be determined. The rotational structure of the (0 2 3) state of HD¹⁸O at 13,245.497 cm⁻¹ is also reported for the first time.     

Pressure shift and broadening of 110-101 water vapor lines by atmosphere gases

This paper is devoted to the measurement of pressure shift and broadening parameters of water-vapor lines of the pure rotational transition 1₁₀-1₀₁ in the ground vibrational state of H₂¹⁶O at 556.936 GHz, H₂¹⁷O at 552.02 GHz, H₂¹⁸O at 547.676 GHz, and the vibrationally excited state v₂=1 line of H₂¹⁶O at 658.003 GHz. The broadening coefficients of the line at 556.936 GHz (for N₂ and O₂ as perturbing gases) coincide within the errors with the values obtained recently by Seta et al. [Pressure broadening coefficients of the water vapor lines at 556.936 and 752.033 GHz. JQSRT 2008;109:144-50] by means of a very different technique (THz-TDS). Pressure shift and broadening for other lines were measured for the first time. Comparison of our results with previous measurements and theoretical calculations is presented.     

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     

Cavity ring-down spectroscopy of H2O in the range 16 570-17 125 cm

Following previous investigations on H₂¹⁶O and H₂¹⁸O by cavity ring-down spectroscopy, this method has now been applied to investigate the energy region of the 5ν polyad in the absorption spectrum of H₂¹⁷O. In the range 16 570-17 125 cm⁻¹, the highest energy range investigated for the H₂¹⁷O isotopologue so far, 516 lines are attributed to H₂¹⁷O and assigned from a newly generated line list.     

Thermal parameters of MgSO4·7H2O and NiSO4·7H2O crystals added with urea and thiourea

Pure and impurity-added (with urea and thiourea) MgSO₄·7H₂O and NiSO₄·7H₂O single crystals were grown by the free-evaporation method from aqueous solutions. Density was measured by the flotation method. X-ray diffraction data were collected for powder samples and used for the estimation of thermal parameters like Debye-Waller factor, mean-square amplitude of vibration, Debye temperature and Debye frequency. The thermal parameters do not vary in a particular order with respect to impurity concentration, which could be attributed to the random disturbance created by the impurity molecules in the hydrogen-bonding system of the MgSO₄·7H₂O and NiSO₄·7H₂O lattices.     

Zero-point spin reduction in a two-dimensional Heisenberg antiferromagnet Cu(HCOO)2 · 4H2O

The copper NMR in a two-dimensional Heisenberg antiferromagnet Cu(HCOO)₂ ·4H₂O (T_N = 17 K) was observed using a standard spin- echo method at liquid He temperatures. The field-dependence of the ⁶³Cu NMR frequency was measured for H₀ (? 56 kOe) | b-axis. The result was interpreted by taking into account a zero-point spin reduction of about 35% in addition to the rotation of the antiferromagnetic spin axis. The amount of the observed spin reduction is in good agreement with the prediction of spin-wave theory.     

Low-uncertainty H2O line intensities for the 930-nm region

We measured room-temperature H₂O spectra of the 3ν polyad within the wave number range 10 603 cm⁻¹ to 10 852 cm⁻¹ using frequency-stabilized cavity ring-down spectroscopy. More than 70 transitions, divisible into two groups based on their relative intensities (strong and weak) were investigated. For the 23 lines comprising the set of strong transitions, the water vapor sample was prepared as a dilute mixture in a steady flow of N₂ carrier gas, and the measurement of the water vapor sample number density was linked to primary methods of humidity generation. For these strong transitions, the measured line intensities were within 1% of previous measurements. The line intensity measurements of the weaker H₂O transitions, were made on samples of static pure water vapor, and these results were systematically greater than previous measurements by approximately 20%.