Infrared Intensities of Liquids XX: The Intensity of the OH Stretching Band of Liquid Water Revisited, and the Best Current Values of the Optical Constants of H₂O(l) at 25°C between 15,000 and 1 cm⁻¹

Abstract

The previously reported nonreproducibility of the intensity of the OH stretching band of liquid water has been explored. It was found that it can be eliminated in measurements with the Circle® multiple ATR cell by ensuring that the ATR rod is coaxial with the glass liquid holder. It was also found that normal laboratory temperature variations of a few degrees change the intensity by ⩽∼1% of the peak height. A new imaginary refractive index spectrum of water has been determined between 4000 and 700 cm1 as the average of spectra calculated from ATR spectra recorded by four workers in our laboratory over the past seven years. It was obtained under experimental and computational conditions superior to those used previously, but is only marginally different from the spectra reported in 1989. In particular, the integrated intensities of the fundamentals are not changed significantly from those reported in 1989. The available imaginary refractive index, k, values between 15,000 and 1 cm−1 have been compared. The values that are judged to be the most reliable have been combined into a recommended k spectrum of H2O(l) at 25 °C between 15,000 and 1 cm−1, from which the real refractive index spectrum has been calculated by Kramers–Kronig transformation. The recommended values of the real and imaginary refractive indices and molar absorption coefficients of liquid water at 25 ± 1 °C are presented in graphs and tables. The real and imaginary dielectric constants and the real and imaginary molar polarizabilities in this wavenumber range can be calculated from the tables. Conservatively estimated probable errors of the recommended k values are given. The precision with which the values can be measured in one laboratory and the relative errors between regions are, of course, far smaller than these probable errors. The recommended k values should be of considerable value as interim standard intensities of liquid water, which will facilitate the transfer of intensities between laboratories.

X-ray emission spectroscopy of bulk liquid water in “no-man’s land”

“…The challenge to this hypothesis is that the x-ray pulse from LCLS is only around 100 fs in duration and the question is if the liquid would have time to undergo any transformation within this time period. A vibrational period in the H-bond translational mode is around 200 fs, 67,68 which is relatively slow in comparison to the pulse length. However, regarding the deposited energy as equivalent to a local heating of the liquid it is most likely the librational mode that will mediate a structural transformation, where the water molecule will rotate out to avoid directional H-bonds.…”

Hydrogen bonds of interfacial water in human breast cancer tissue compared to lipid and DNA interfaces

“…The double structure occurs also in IR spectrum of water. The IR spectrum of bulk water has also two components [89][90][91]: at about 3400 cm -1 and a weak shoulder at about 3250 cm -1 . The Raman spectrum of the bulk water in Figure 4 represents the spectrum recorded without the polarization analyzer.…”

Aqueous solvation dynamics studied by photon echo spectroscopy

“…[16][17][18][19][20] Experimentally, time-domain techniques such as fluorescence up-conversion, 2 optical Kerr effect ͑OKE͒ [3][4][5] and THz spectroscopy, 6,7 in addition to frequency-domain spectroscopies such as Raman [8][9][10] and infrared ͑IR͒ [11][12][13][14][15] have been employed to gain a detailed understanding of the intermolecular and intramolecular motions and dynamics of liquid water. Theoretical studies of aqueous solvation 16 have included simulations ranging from predictions of the IR and Raman spectra, [20][21][22][23] to calculations of the solvation relaxation function S(t), 17,19,23,24 and the third order response.…”

“…However, its appearance in the far IR is more controversial. 6,15,22 The experimental data 13,14 used to calculate the spectral density in this range resolves a broad and very weak shoulder on the 200 cm Ϫ1 band at 50 cm…”