EXPERIMENTAL AND THEORETICAL STUDY OF THE H2OHF COMPLEX IN THE GAS PHASE. COMPLETELY NONEMPIRICAL CALCULATION OF THE n(HF) BAND STRUCTURE.

V.P. BULYCHEV, E.I. GROMOVA, AND K.G. TOKHADZE

The n (HF) band profile in H2O...HF hydrogen-bonded complex was studied in the gas phase at T=293 K. The spectra of the HF/2O gaseous mixtures were recorded in the 4200-3000 cm-1 spectral region with a Bruker 120 FTIR spectrometer at 0.2-0.02 cm-1 resolution using the stainless steel cell (L=20 cm) with sapphire windows. The spectra of H2O..HF complex in the region of the n 1(HF) absorption band were obtained by subtracting the calculated spectra of free H2O and HF molecules from the experimental spectrum. The n 1 band of the H2OHF complex has an asymmetric shape with a low-frequency head, an extended high-frequency wing, and the characteristic vibrational structure. Two variants of reconstruction of the n 1 band shape as a superposition of vibration-rotational bands of the fundamental and hot transitions were considered. A simplified semiempirical procedure was used in the first variant. The second variant was based on a nonempirical anharmonic calculation of the vibrational level energies,the frequencies and intensities of corresponding transitions and the rotational constants. These parameters were determined by an ab initio SCF MP2 calculation of surfaces of the potential energy and of the dipole moment and a variational solution of one-, two-, and three-dimensional anharmonic vibrational problems. The absorption spectrum in the 3720-3600 range, reconstructed with the use of the nonempirical electrooptical parameters, sufficiently well reproduces the main characteristics of the experimental spectrum, in particular, the relative intensities of maxima of the vibrational structure. However, the interpretation of most of the structural features of the spectrum differs from that assumed in the semiempirical scheme. Above all, it follows from the results of the nonempirical calculation that the n1=10 transition from the ground vibrational state should be associated with the central, most intense maximum of the experimantal spectrum. Allowance for this fact leads to a new value of vibrational transition frequency n10 in the H2O..HF complex equal to 3635 m-1, which is higher than the commonly accepted value of 3608 m-1.

 




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2. - NF3 + AR

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4.CRYOSPECTRA OF HYDROGEN DEUTERIDE DISSOLVED IN LIQUID NEON: NEW EFFECTS AND THEIR INTERPRETATION.

5. - (SF6)2 (SiF4)2. (1-3) Ar (11)

6. n1 ~ 2 n4 CHF3 .

7.DENSITY EVOLUTION OF THE ps TIME-DOMAIN CARS RESPONSES FROM THE CO2 GAS.

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9. SF6 CF4 .

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