Correlated libration in liquid water.

The libration spectrum of liquid H2O is resolved into an octupolar twisting libration band at 485 cm-1 and dipolar rocking-wagging libration bands at 707 and 743 cm-1 using polarization analysis of the hyper-Raman scattering (HRS) spectrum. Dipole interactions and orientation correlation over distances less than 2 nm account for the 36 cm-1 splitting of the longitudinal and transverse polarized bands of the dipolar rocking-wagging libration mode, while the intensity difference observed for the bands is the result of libration correlation over distances larger than 200 nm. The coupled rock and wag libration in water is similar to libration modes in ice. The libration relaxation time determined from the width of the spectrum is 36-54 fs. Polarization analysis of the HRS spectrum also shows long range correlation for molecular orientation and hindered translation, bending and stretching vibrations in water.

Long-range correlation of intra-molecular and inter-molecular vibration in liquid CCl4.

Experiments measuring the polarization dependence of hyper-Raman light scattering reveal long-range correlation of molecular vibrations in liquid CCl4. The ν3 and ν1 + ν4 intra-molecular vibrations at about 770 cm-1 are strongly polarized transverse to the scattering wavevector. Weaker transverse polarization is exhibited by the ν1, ν2, and ν4 intra-molecular vibrations and by the inter-molecular collision-induced band around 0 cm-1. The observed polarization dependence is due to the correlation of the vibrations on molecules separated by about 200 nm. The strength of the observed correlation increases with the transition dipole moment for the vibration mode and is consistent with dipole-dipole coupling.

Vibration overtone hyperpolarizability measured for H2.

The second hyperpolarizability (γ) of the H2 molecule was measured by gas-phase electric field induced second harmonic generation at the frequencies of the one-photon resonance for the 3-0 Q(J) overtone transitions (v, J = 0, J → 3, J for J = 0, 1, 2, and 3). The magnitude of the resonant contribution to γ was measured with 2% accuracy using the previously determined non-resonant γ for calibration. Pressure broadening and frequency shift for the transitions were also measured. A theoretical expression for the resonant vibrational γ contribution in terms of transition polarizabilities is compared to the observations. The measured γ resonance strength is 4%-14% larger than the results obtained from this theoretical expression evaluated using ab initio transition polarizabilities.

Third harmonic scattering in liquids.

Third harmonic scattering (THS) from liquids has been observed and analyzed in several recent papers. It is considered to be analogous to second harmonic scattering (hyper-Rayleigh scattering) and to provide a means for measuring the second hyperpolarizability tensor of molecules in a liquid. However, the observed signal for a pure solvent is in fact mainly due to coherent third harmonic generation followed by Rayleigh scattering and direct incoherent THS (direct THS) makes only a small contribution (<2% for parallel polarized THS). This invalidates the internal reference method and the polarization analysis that has been applied for pure liquids. Theoretical comparison for the two processes, extensive experimental measurements for CCl4 liquid, SiO2 glass, and CCl2F2 gas and survey measurements for D2O, CDCl3, CD3CN, and (CD3)2SO liquid, are presented.

Response to "Comment on 'Water-water correlations in electrolyte solutions probed by hyper-Rayleigh scattering'" [J. Chem. Phys. 149, 167101 (2018)].

The Comment proposes that the discrepancy between two second harmonic scattering (SHS) experiments for D2O electrolyte solutions with 100 ns and 190 fs laser pulses is due to unexplained processes for 100 ns pulses that give non-quadratic power dependence for the second harmonic signal. However, the different power dependence of the second harmonic scattering signals measured with 100 ns and 190 fs laser pulses is due to changes in laser beam propagation and focal intensity caused by the combined effect of thermal defocusing and Kerr lens self-focusing. Non-quadratic power dependence does not explain the discrepancy in the second harmonic scattering results.

What is measured by hyper-Rayleigh scattering from a liquid?

Polarization and angle dependence of hyper-Rayleigh scattering (HRS) measured for liquid acetonitrile and dimethyl sulfoxide (DMSO) is analyzed in terms of contributions from randomly oriented molecules and additional contributions produced during intermolecular collisions and induced by the electric field of dissolved ions. All three contributions show the effect of long-range correlation, and the correlation functions are determined using the HRS observations combined with the results of molecular dynamics simulations. HRS from acetonitrile is polarized transverse to the scattering vector. This is due to long-range molecular orientation correlation produced by the dipole-dipole interaction, and correlation at distances r > 100 nm must be included to account for the HRS observations. Analysis of the HRS measurements for acetonitrile determines the length scale a = 0.185 nm for the long-range longitudinal and transverse orientation correlation functions BL=-2BT=a3/r3. Transverse polarized collision-induced HRS is also observed for acetonitrile, indicating long-range correlation of intermolecular modes. Strong longitudinal HRS is induced by the radial electric field of dissolved ions in acetonitrile. For DMSO, the angle between the molecular dipole and the vector part of the first hyperpolarizability tensor is about 100°. As a result, HRS from the randomly oriented molecules in DMSO is nearly unaffected by dipole correlation, and ion-induced HRS is weak. The strong longitudinal polarized HRS observed for DMSO is due to the collision-induced contribution, indicating long-range correlation of intermolecular modes. The HRS observations require correlation that has r-3 long-range asymptotic form, for molecular orientation and for intermolecular vibration and libration, for both acetonitrile and DMSO.

Structural correlation in water probed by hyper-Rayleigh scattering.

Second-harmonic or hyper-Rayleigh scattering (HRS) is sensitive to molecular interactions and correlations, and there is a large coherent HRS contribution for water. This work shows that the distinctive angle and polarization dependence observed for HRS from water is due to the long-range orientation correlation of the molecules. The results of HRS experiments for water are analyzed in combination with a molecular dynamics simulation to determine the molecular hyperpolarizability and the short-range and long-range orientation correlation functions for the molecules. At long range, the longitudinal and transverse dipole-dipole orientation correlation functions are BL(r) = -2BT(r) = a3/r3 with a = 0.166 nm. Molecular correlation at distances r > 100 nm must be included to account for the HRS observations.

Water-water correlations in electrolyte solutions probed by hyper-Rayleigh scattering.

Long-range ion-induced correlations between water molecules have been observed by second-harmonic or hyper-Rayleigh scattering experiments with conflicting results. The most recent work observed a large difference between the results for H2O and D2O, and large discrepancies with the previously proposed theory. However, the present observations are in quantitative agreement with the model where the ion electric field induces second harmonic generation by the water molecules, and ion-ion correlations given by the Debye-Huckel theory account for intensity saturation at high ion concentration. This work compares experimental results with theory and addresses the apparent discrepancies with previous experiments.

Orientation correlation and local field in liquid nitrobenzene.

Hyper-Rayleigh scattering (HRS) is sensitive to long-range molecular orientation correlation in isotropic liquids composed of dipolar molecules. Measurements of the polarization, angle, and spectral dependence for HRS from liquid nitrobenzene (NB) are analyzed to determine the NB molecular orientation correlations at long range. The longitudinal and transverse orientation correlation functions for r > 3 nm are BL(r) = (a/r)(3) and BT(r) = - BL(r)/2, where a = 0.20 ± 0.01 nm. Measurements of HRS induced by dissolved ions are also analyzed and combined with molecular dynamics simulation and dielectric response results, to determine the molecular dipole moment µ = 3.90 ± 0.04 D, Kirkwood orientation correlation factor gK = 0.68 ± 0.02, and local field factor f(0) = 0.85 ± 0.04 × Onsager local field factor in liquid nitrobenzene.

Long-range orientation correlation in dipolar liquids probed by hyper-Rayleigh scattering.

Hyper-Rayleigh scattering (HRS) is sensitive to long-range molecular orientation correlation in isotropic liquids composed of dipolar molecules. The correlation functions that appear in the calculation of HRS mediated by the vector part of the first hyperpolarizability ß are the same as the correlation functions for the homogeneous isotropic random vector fields that appear in the description of fluid turbulence. Recent experiments measuring the angle and polarization dependence of HRS from water find a dominant transverse mode contribution with amplitude independent of the scattering wavevector, and this observation of transverse mode HRS strongly constrains the form of the orientation correlation function. Analysis of these HRS results for water determines that the long-range molecular orientation correlation function varies as r(-3±Îµ) with |ε| < 0.03 on spatial scales up to 2000 nm.

Hyperpolarizability dispersion measured for (CH3)2O.

The third-order nonlinear-optical susceptibility of dimethyl ether, (CH3)2O, has been measured in the gas phase over the wavelength range 488 nm < λ < 1064 nm using the technique of gas-phase electric-field-induced second-harmonic generation with periodic phase matching and with N2 as the reference gas. Measurements span a range of temperature, which allows for separation of the temperature-independent second hyperpolarizability term from the temperature-dependent first hyperpolarizability term. The dispersion curves of the isotropically averaged first and second hyperpolarizabilities (ß and γ) are deduced.

Long-range orientation correlation in water.

Strong short-range intermolecular interactions result in position and orientation correlations between nearest neighbour molecules in isotropic liquids, but it is generally assumed that such correlations extend at most a few molecular diameters. Results from second-harmonic light scattering experiments presented here reveal long-range molecular orientation correlations in liquid water, where the molecular dipole orientation distribution has the form of a nearly pure transverse vector field. Spatial scales in the range 200-2000 nm are probed by the angle-dependent measurements and the observed correlations are thought to result from rotation-translation coupling in acoustic phonons in the liquid.

Magnetometry in a diamond anvil cell using nitrogen vacancy centers in a nanodiamond ensemble.

The emerging field of optical magnetometry utilizing negative-charged nitrogen vacancy (NV-) centers provides a highly sensitive lab bench technique for spatially resolved physical property measurements. Their implementation in high pressure diamond anvil cell (DAC) environments will become common as other techniques are often limited due to the spatial constraints of the sample chamber. Apparatus and techniques are described here permitting for more general use of magnetic field measurements inside a DAC using continuous wave optical detected magnetic resonance in NV- centers in a layer of nanodiamonds. A microstrip antenna delivers a uniform microwave field to the DAC and is compatible with simple metal gaskets, and the sensor layer of deposited nanodiamonds allows for simple determination of the magnetic field magnitude for B in the 1-100 G range. The ferromagnetic transition in iron at 18 GPa is measured with the apparatus, along with its hysteretic response.

Orientation correlation of p-nitroaniline molecules in acetone solution observed by hyper-Rayleigh scattering.

Measurements of the polarization dependence of hyper-Rayleigh scattering (HRS) by solutions of p-nitroaniline (PNA) in acetone-d6 were used to study molecular orientation correlations. The HRS observations were analyzed in terms of short range direct dipole-dipole correlations between the PNA molecules, a long range transverse polar mode for the PNA molecules, and a long range ion-induced longitudinal polar mode. The conclusion that long range correlations are present is opposite to that in previous work, due to previous neglect of the ion-induced contribution. Depolarized HRS not explained by local correlations appears above 0.1 M PNA concentration, and analysis of the HRS observations indicates strong orientation correlations with a range of 10 nm for the PNA molecules.

Hyper-Rayleigh scattering from correlated molecules.

The polarization dependence of hyper-Rayleigh scattering has been calculated for spherical domains of orientation correlated molecules. Distributions with radial or azimuthal mean polar orientation of the molecules are found that give results consistent with experimental observations, and expressions for the polarization ratios in terms of the product of correlation strength and correlated domain size are derived for these distributions. Assuming a plausible correlation strength, it is estimated that the correlated domain size in typical polar liquids is of order 100 molecular diameters.

Effect of composting on the fate of steroids in beef cattle manure.

In this study, the fate of steroid hormones in beef cattle manure composting is evaluated. The fate of 16 steroids and metabolites was evaluated in composted manure from beef cattle administered growth promotants and from beef cattle with no steroid hormone implants. The fate of estrogens (primary detected as estrone), androgens, progesterone, and the fusarium metabolite and implant α-zearalanol was monitored in manure compost piles. First-order decay rates were calculated for steroid half-lives in compost and ranged from 8 d for androsterone to 69 d for 4-androstenedione. Other steroid concentration data could not be fit to first-order decay models, which may indicate that microbial processes may result in steroid production or synthesis in composting systems. We demonstrate that composting is an effective strategy to remove steroid hormones from manure. Total steroid hormone removal in composted beef cattle manure ranged from 79 to 87%.

Effect of growth promotants on the occurrence of endogenous and synthetic steroid hormones on feedlot soils and in runoff from beef cattle feeding operations.

Supplements and growth promotants containing steroid hormones are routinely administered to beef cattle to improve feeding efficiency, reduce behavioral problems, and enhance production. As a result, beef cattle manure will contain both synthetic steroids as well as a range of endogenous steroids including androgens, estrogens, and progestogens. A two-year controlled study was conducted in which beef cattle were administered steroid hormones via subcutaneous implants and feed additives and the occurrence of 16 endogenous and synthetic steroid hormones and metabolites was evaluated in runoff from beef cattle feedlots and in manure and soil collected from feedlot surfaces. Samples were extracted and analyzed using liquid chromatography tandem mass spectrometryfor metabolites of the synthetic androgen trenbolone acetate, 17α-trenbolone, 17ß-trenbolone, for the nonsteroidal semisynthetic estrogen agonist, α-zearalanol, and the synthetic progesterone melengesterol acetate, as well as a wide range of endogeneous estrogens, androgens, and fusarium metabolites. Synthetic steroids including trenbolone metabolites and melengestrol acetate were detected in fresh manure and in feedlot surface soils from cattle administered synthetic steroids at concentrations up to 55 ± 22 ng/g dry weight (dw) (17α-trenbolone) and 6.5 ± 0.4 ng/g dw (melengesterol acetate). Melengesterol acetate was detected in 6% of runoff samples from feedlots holding cattle administered synthetic steroids at concentrations ranging up to 115 ng/L. The presence of melengesterol acetate in runoff from beef cattle feeding operations has not been previously reported. Synthetic steroids were not detected in manure or runoff from control cattle. A wide range of endogenous hormones were detected in runoff and feedlot surface soils and manure from cattle given synthetic steroids and from control cattle, with no statistically significant differences in concentration. These results indicate that runoff from confined animal production facilities is of environmental and public health concern regardless of the use of growth promotants.

Gas phase hyper-Rayleigh scattering measurements.

Measurements of hyper-Rayleigh scattering intensities and polarization ratios are presented for nine small molecules in the gas phase [CH(4), CF(4), CCl(4), N(2)O, NH(3), D(2)O, SO(2), CF(2)Cl(2), and (CH(3))(2)CO]. In four cases [CH(4), CF(4), CCl(4), and N(2)O] all molecular hyperpolarizability tensor components can be determined from the measurements. The results of this experiment are compared with the results of previous ab initio calculations, finding discrepancies up to 60%. Including vibrational contributions decreases the discrepancies for CH(4) and CF(4) and increases them for CCl(4), D(2)O, and NH(3).