On the possibility of enrichment of H2O nuclear spin isomers by adsorption

Experimental data on the enrichment of H₂O nuclear spin isomers by means of adsorption, as suggested in several works by other authors, are reported. We were unable to observe any enrichment of isomers. The conclusion was drawn that the adsorption characteristics of water ortho and para isomers were insignificantly different. An analysis of the relaxation of H₂O spin isomers induced by the intramolecular mixing of the molecular ortho and para spin states and caused by collisions with paramagnetic oxygen molecules was performed.     

Spectroscopic evidence for the effect of the ortho H<Subscript>2</Subscript>O spin on the electron transfer in photosynthesis

A spin mechanism for electron transfer control in the reaction center of purple bacteria in photosynthesis is proposed. Rotation and conversion of the ortho/para spin isomers of two H₂O molecules located near the special pair of the reaction center are treated as the sources of the coherent modulations of transient kinetics. Modulation of the collective wave function of the reaction center electrons by the total proton spin of ortho H₂O is a key feature allowing the molecule to play the role of a gate controlling the electron transfer. The iron atom in the reaction center with the gradient magnetic field is treated as a catalyst removing the strict forbiddenness of H₂O ortho/para conversion. It is shown that the modulation of the reaction center stimulated emission kinetics observed in the field of femtosecond pulses coincides with the rotational transitions of ortho/para H₂O. Influence of the effect of the electric field (Stark effect) on the level displacement and ortho/para conversion rate is discussed.     

Observation of rotational resonances of ortho and para spin isomers of the H<Subscript>2</Subscript>O molecule in hexagonal ice using four-photon laser spectroscopy

Rotational resonances of ortho and para spin isomers of the H₂O molecule are observed in hexagonal ice using four-photon spectroscopy of coherent light scattering. It is experimentally shown that the resonant contribution to the four-photon scattering signal from para H₂O spin isomers in ice is about half as large as that in the liquid phase.     

Conversion of ortho-para H2O isomers in water and a jump in erythrocyte fluidity through a microcapillary at a temperature of 36.6±0.3°C

A mechanism is proposed for the previously observed [1] jump in erythrocyte fluidity through a microcapillary 1.3 μm in diameter at a temperature of 36.6±0.3°C. Our interpretation is based on the experimental evidence both for existence of ortho and para H₂O isomers in water and on spin-selective interaction of proteins with para H₂O isomers as hydration shells of biomolecules are being formed [2]. It is important that the formation of hydration shells of proteins and DNA in aqueous solutions is accompanied by an increase in the Brillouin shift to 0.4 cm⁻1 (≃0.25 cm⁻¹ in water), which points to the formation of icelike structures. We believe that the coincidence of the translational energy kT of the Brownian motion and the energy of the rotational quanta for the 3₁₃–2₀₂ transition of para H₂O isomers at the temperature 36.6°C increases the probability for excitation of para H₂O isomers in collisions. Collisions mix quantum states of closely spaced levels in para H₂O (3₁₃, 285.2 cm⁻¹) and ortho H₂O (3₃₀, 285.4 cm⁻¹) and induce conversion of para isomers to ortho H₂O. It is assumed that this conversion in the icelike hydration shell of hemoglobin (Hb) is accelerated under the catalyzing effect of oxygen and iron present in Hb and triggers a chain reaction: release of ortho H₂O isomers through the erythrocyte membrane→compaction of Hb molecules and increase in concentration of catalysts→acceleration of conversion→structural gel-sol transition. It is the sequence of these processes that provides a jump in fluidity of erythrocytes through a microcapillary and the anomalous increase in fluidity of the aqueous solution of hemoglobin by almost an order of magnitude at temperatures close to 36.6°C and an increase in the solution concentration by a factor of 1.7.     

Coherent laser spectroscopy of RF resonances in liquid

Four-photon polarization spectra of double distilled water subjected to a special treatment in a cavitation chamber and 20% aqueous solution of hydrogen peroxide were recorded in the range ±8 cm⁻¹. All recorded spectra contain narrow (< 0.3 cm⁻¹) resonances corresponding to the frequencies of the rotational spectrum of ortho and para spin isomers of the H₂O molecule. Numerical simulation of the spectra obtained made it possible to quantitatively estimate the contribution of the rotational spectrum to the coherent scattering signal. It was found that the contribution of the para spin isomer of the H₂O molecule to the rotational line spectrum decreases in an aqueous solution of the α-chymotrypsin protein. Apparently, this decrease indicates the selectivity of interaction of biopolymer molecules with different spin isomers.     

BWO spectroscopy of water spin isomers based on desorption from glycerol

Violation of the normal spin 3: 1 ortho/para ratio in saturated water vapor above a 0.5% water-glycerol solution was detected using the BWO spectroscopy method. The solution was prepared by pumping the initial solution out at room temperature. The effect is supposed to be due to increased fugacity of ortho water molecules from the solution and the corresponding para enrichment of residual water.     

Selective adsorption of water spin isomers under laser excitation

The experiment on water molecule adsorption on the surface of nanoporous polymeric adsorbent in the Knudsenmode under conditions of selective action of IR radiation is described. Resonant excitation of the vibrational-rotational transition of the ortho-modification of H₂O molecules at a wavelength of 1.85 µm is used. The applicability of this method to the production of water vapor with nonequilibrium concentration ratios of ortho and para modifications of water molecules is shown.     

Coincidence of rotational energy of H<Subscript>2</Subscript>O ortho-para molecules and translation energy near specific temperatures in water and ice

A hypothesis of the quantum nature of the specific temperatures T _s of water and ice, whose values is not random, was formulated. It was found that the quantum energy hΩ _mn of closely located rotational transitions in the ortho and para spin isomers of H₂O molecules coincides with the translation energy kT near the well-known specific temperatures T _s in ice and water. On the basis of this fact it was suggested that ortho-para conversion occurs at temperatures close to T _s upon inelastic collisions and resonance energy exchange kT _s ↔ hΩ _mn in the rotation-translation-rotation (RTR) processes. Such conversion can induce rearrangement of the H-bond set structure and repacking of H₂O molecules. The coincidence kT _s ≈ hΩ _mn was checked for ice and water at 12 known T _s, as well as for heavy water D₂O near T _s = 11.2°C (maximum density) and −140°C (glassy transition). The previously observe strong deformation of the OH Raman band near T _s = 4, 19, 36, and 76°C (maximum density, maximum surface tension, minimum heat capacity, and maximum speed of sound, respectively) was interpreted as a manifestation of the water structure rearrangement induced by H₂O ortho-para conversion.     

Azurin-Solvent interaction: an ESR spin labeling investigation

We have investigated by means of electron spin resonance (ESR) spectroscopy using two spin labels, Iodoacetamido-proxyl and 3-Maleimido-proxyl, the dynamics of two different regious around the active site of azurin, a copper containing blue protein. The ESR measurements of spin labeled azurin have been carried out in the 110–300 K temperature range on wet (H₂O, D₂O and ethanol/water mixtures) and lyophilized samples. The behaviours of the outer hyperfine splitting separation, 2A′ _zz , of the ESR spectravs temperature of the lyophilized, and fully hydrated azurin in H₂O and D₂O suggest that the two spin labels are located in regions of the protein surface with different dynamics and polarity. Moreover, all differences in the 2A′ _zz values shown by the spin labeled azurin in normal and heavy water as well as the temperature behaviour disappear when azurin is in ethanol/water mixtures. The results are discussed in terms of a close correlation between the molecular dynamics of the protein fragments to which the two spin labels are bound and the properties of the solvent used.     

Zeeman relaxation of N2 + (2Σ+) in collisions with 3He and 4He

We compare the cross sections for the transitions changing the projection of the total angular momentum of N₂ ⁺(²Σ) in collisions with ³He and ⁴He at very low collision energy. The fundamental states of the two nuclear spin isomers of N₂ ⁺ are considered as well as the two fine structure levels of the first excited para level N=2. It is shown that the two fundamental states of the two nuclear spin isomers behave differently. For the fundamental para level N=0 of N₂ ⁺, the projection changing cross section is always negligible compared to the elastic one for both He isotopes. For the fundamental ortho level N=1 of N₂ ⁺, the spin-rotation interaction couples the different spin levels directly so the spin relaxation becomes a first order process. The associated resonances increase the projection changing cross section which remains smaller but becomes comparable with the elastic one. This is in contrast with the excited rotational levels of N₂ ⁺, which for the rotational deactivation and elastic channels are found to be equal around the resonances for the collisions involving ³He. These two channels are always larger than the projection changing one. We also find that, for transitions involving the fundamental rotational state, the domain of validity of the threshold laws discussed by Krems and Dalgarno [Phys. Rev. A 67, 050704 (2003)] for a potential decreasing faster than 1/r2 is shortened, due to the long range charge induced dipole potential. This effect is illustrated for the collisions of ³He with the fundamental para state of N₂ ⁺.     

The temperature dependence of the viscomagnetic effect in the hydrogen isotopes

Experiments have been performed on the viscosity change of para and normal H₂, and ortho and normal D₂, under the influence of a magnetic field. This viscomagnetic effect is investigated as a function of the temperature between 140 K and room temperature. The data of this work are expressed in terms of effective cross sections for several elastic and inelastic collision processes. A comparison is made with results for HD, as obtained by Burgmans.     

Anomalous Ortho-to-Para Ratio of Nuclear Spin Isomers of H2O at Low Temperatures

A theoretical model proposed for nuclear spin isomers of H₂O molecules located inside the C₆₀ fullerene explains an anomalously high stability of ortho-H₂O isomers detected in the experiments reported in [B. Meier et al., Nature Commun. 6, 8112 (2015)] at a temperature of T = 5 K.

     

Laser analysis of the relative content of ortho- and para-water molecules for the diagnostics of spin-selective processes in gaseous media

The physical principles of laser spectral analysis of the relative content of ortho- and para-water molecules, which is aimed at studying the spin-selective processes in gaseous media, are considered. An analyzer of the content of water spin isomers is described. It is based on a tunable diode laser and implies high-precision measurement of the near-IR absorption in vibrational-rotational lines of the H₂O molecule. The efficiency of the diagnostic method developed is demonstrated in the diagnostics of spin-selective adsorption in nanoporous polymer sorbents. There was confirmed the existence of the effects of spin-selective adsorption of ortho- and para-water molecules, which had been previously observed by only submillimeter spectroscopy.     

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.     

Spin solitons in molecular magnetic materials with the chiral structure

Quasiperiodic sequences of the maxima of microwave absorption with decreasing amplitudes have been observed in a temperature range of 4–50 K in the electron spin resonance spectra of ferrimagnetic chiral single crystals [Mn{(R/S)-pn}]₂[Mn{(R/S)-pn}₂(H₂O)][Cr(CN)₆]₂, as well as [Cr(CN)₆][Mn(S)-pnH-(H₂O)]H₂O. Theoretical estimates and previous experimental data indicate that the Dzyaloshinskii-Moriya interaction is the main factor determining the chirality of the spin density and the existence of soliton solutions for the spin dynamics in these crystals. The experimental dependences obtained for the distances between the microwave power absorption maxima on the constant component of the magnetic field of the spectrometer correspond to the theoretical predictions for spin solitons in three-dimensional magnetic materials and exhibit another behavior in crystals with quasi-two-dimensional magnetic ordering.     

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.     

Oxygen-17 NMR Spectroscopy: Effect of Substituents on Chemical Shifts and Width Line in Ortho Substituted Nitro Benzenes

¹⁷O-NMR spectra, of ortho, meta and para substituted nitrobenzene are reported. The ¹⁷O nucleus of NO₂ group in ortho derivatives absorb at lower field that meta and para compounds. Moreover, width line of ¹⁷O resonance appears to be strongly dependent by substituent position. The ¹⁷O chemical shifts are correlated with U. V. spectra and X-ray diffraction data.     

Water in planetary and cometary atmospheres: H2O/HDO transmittance and fluorescence models

We developed a modern methodology to retrieve water (H₂O) and deuterated water (HDO) in planetary and cometary atmospheres, and constructed an accurate spectral database that combines theoretical and empirical results. On the basis of a greatly expanded set of spectroscopic parameters, we built a full non-resonance cascade fluorescence model and computed fluorescence efficiencies for H₂O (500 million lines) and HDO (700 million lines). The new line list was also integrated into an advanced terrestrial radiative transfer code (LBLRTM) and adapted to the CO₂ rich atmosphere of Mars, for which we adopted the complex Robert–Bonamy formalism for line shapes. We retrieved water and D/H in the atmospheres of Mars, comet C/2007 W1 (Boattini), and Earth by applying the new formalism to spectra obtained with the high-resolution spectrograph NIRSPEC/Keck II atop Mauna Kea (Hawaii). The new model accurately describes the complex morphology of the water bands and greatly increases the accuracy of the retrieved abundances (and the D/H ratio in water) with respect to previously available models. The new model provides improved agreement of predicted and measured intensities for many H₂O lines already identified in comets, and it identifies several unassigned cometary emission lines as new emission lines of H₂O. The improved spectral accuracy permits retrieval of more accurate rotational temperatures and production rates for cometary water.     

Origin of the NMR signal in liquid water

An experimental method for testing alternative hypotheses about the origin of the NMR signal in liquid water, i.e., whether it is generated by (a) protons 1H with spin 1/2 of H₂O molecules or (b) orthomolecules with spin 1, containing parallel spins and constituting three-quarters of the total number of H₂O molecules, is proposed.     

Hydration-induced conformational changes in protonated 2,4-pentanedione in the gas phase

Starting with H⁺[CH₃C(O)CH₂C(O)CH₃] (denoted H⁺PD), the protonated diketone-water clusters H⁺PD(H₂O) _n (n = 1–3) have been characterized by density functional theory calculations in combination with vibrational predissociation spectroscopy to explore the conformational changes of a protonated bifunctional ion solvated by water in the gas phase. Theoretical calculations for H⁺PD revealed that the ion contains an intramolecular hydrogen bond (IHB), with two oxygen atoms bridged by the extra proton in an O—H⁺ … O form. Attachment of one water molecule to it readily ruptures this IHB, replacing the H⁺ by the H₃O⁺ moiety. Further replacement of the IHB by two water molecules occurs at n = 2 and the ?C(O)CH₂C(O)- chain is fully opened (or unfolded) after transfer of the extra proton to the water trimer at n = 3. To verify the computational findings, infrared spectroscopic measurements were performed using a vibrational predissociation ion trap spectrometer to identify cluster isomers from the signatures of hydrogen bonded and non-hydrogen bonded OH stretching spectra of H⁺PD(H₂O)_2,3 produced in a corona discharge supersonic expansion. Besides open form isomers, evidence for the formation of water-bridged structures has been found for H⁺PD(H₂O)₃ at an estimated temperature of 200 K. A detailed illustration of the unfolding steps as well as the energy profiles for the evolution of a two-water bridge isomer from the protonated H⁺PD monomer are analysed pictorially (including both stable intermediates and transition states) in the present investigation.