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High-density amorphous ice (HDA) , made by compression of hexagonal ice at 77K, was heated at a constant pressure of 0.81 GPa upto 195 K and its phase transition followed by displacement-temperatures curves. Conversion of HDA into either ice IV or ice XII is an example of a 'parallel reaction' where the relative yields of ice IV and ice XII could be controlled by temperature.

The research demonstrates that, depending on temperature, protein exchange occurs in three ways. This is illustrated by using a benchmark calculation on the concerted proton transfer in cyclic (HF)n (n=4, 5) oligomers.

Research was conducted to examine a fully ab initio-dual reaction path dynamics measurement of the synchronous proton exchange in carboxylic acid dimers that is consistent with experimental findings. The transfer reaction of systems containing one (HD) and two (DD) deuterons instead of the carboxylic protons were investigated. Results provide the first correlated calculation of the exchange barrier in the benzoic acid dimer.

An approach based on the variational transition state theory was employed in computing reaction rate constants for cyclic hydrogen fluoride cluster's concerted proton transfer. (HF)5, which is similar to carboxylic acid dimers, exhibited a reaction rate constant of k(300 K) + 2.86 c 10(super 9)s-1. The importance of the concerted proton exchange motion is seen in various experimental and theoretical studies of carboxylic acids.

Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction have shown that the two crystal polymorphs [alpha]-[H.sub.2]C[O.sub.3] and [beta]-[H.sub.2]C[O.sub.3] are formed from two different amorphous states, indicating polyamorphism for [H.sub.2]C[O.sub.3]. The studies have shown that the two amorphous states of [H.sub.2]C[O.sub.3] are connected by a first order-like phase transition.

A detailed investigation of the interaction of HCl with a variety of ice surfaces shows that the nature of the HCl-ice interaction is critically dependent on the characteristics of the ice substrate.

A novel method of detecting the glass -> liquid transition at high pressures which comprises measuring the relative volume change incurred upon heating glassy samples into the liquid state is reported.

The mechanism of formation of sulfonate ion from the solutions of sulfur dioxide is shown by ab initio and transition state theory considerations. It is demonstrated that the equilibrium process between the two ions, bisulfite ion HOSO2- and the sulfonate ion HSO3-, is a two-step mechanism.

It has been studied that the relaxation from BII state is much faster with high rate constants and depending on temperature. The structures of the B1 DNA seem similar to the x-ray crystallography than the all BII state.

Research has been conducted on aquacopper(II) bis(amino acid) complexes with sarcosine and glycine. The authors describe the vacuum structures of these complexes using B3LYP method.

High-density (HDA) amorphous ice was heated to prepare ice IV in a reproductible manner. This enabled to measure the development of peak-positions and phase transition from ice IV to ice I.

The reaction rates for the transformation of HOCl by HCl and HBr into Cl2 and BrCl, respectively, aided by n = 0,1,2, and 3 water molecules are presented. The reaction rates were ascertained using canonical, variational transition phase theory including tunneling revisions for motion along the reaction coordinate.

The mechanistic features of water-mediated proton transfer in the isomerization reaction in hydrogen-bonded sulfur oxide-water supermoleucules is described. The protons are asynchronously transferred according to the hydrogen-bond compression mechanism, which force the reaction to be classical instead of quantum-tunneling-dominated down to rather low temperatures.

We present an experimental method aimed at measuring mass densities of solids at ambient pressure. The principle of the method is flotation in a mixture of liquid nitrogen and liquid argon, where the mixing ratio is varied until the solid hovers in the liquid mixture. The temperature of such mixtures is in the range of 77–87 K, and therefore, the main advantage of the method is the possibility of determining densities of solid samples, which are instable above 90 K. The accessible density range (∼0.81–1.40 g cm–3) is perfectly suitable for the study of crystalline ice polymorphs and amorphous ices. As a benchmark, we here determine densities of crystalline polymorphs (ices Ih, Ic, II, IV, V, VI, IX, and XII) by flotation and compare them with crystallographic densities. The reproducibility of the method is about ±0.005 g cm–3, and in general, the agreement with crystallographic densities is very good. Furthermore, we show measurements on a range of amorphous ice samples and correlate the density with the dspacing of the first broad halo peak in diffraction experiments. Finally, we discuss the influence of microstructure, in particular voids, on the density for the case of hyperquenched glassy water and cubic ice samples prepared by deposition of micrometer-sized liquid droplets. [ABSTRACT FROM AUTHOR]

Unraveling methanol's infrared spectrum has challenged spectroscopists for a century, with numerous loose ends still to be explored. We engage in this exploration based on experiments of isolating single methanol molecules in solid argon and neon matrices. We report infrared spectra of methanol in its natural isotopic composition and with partial and full deuteration. These experiments are accompanied by calculating wavenumbers involving anharmonicity and mode-coupling based on the vibrational configuration interaction approach. This allows for an unambiguous assignment of all fundamentals and resonances in the mid-infrared spectrum. An increasing degree of deuteration lifts resonances and aids in assigning bands uniquely. It also becomes evident that different notations typically used in chemistry or physics to describe molecular vibration from spectroscopy fail to describe the spectra appropriately. We highlight the shortcomings and suggest a more elaborate analysis using Sankey diagrams to unambiguously identify spectral features. Consequently, we demystify debated resonances occurring from various stretches and deformations of the methyl group., Competing Interests: The authors declare no competing financial interest., (© 2024 The Authors. Published by American Chemical Society.)

The preparation of pure cubic ice without hexagonal stacking faults has been realized only recently by del Rosso et al. ( Nat. Mater. 2020, 19, 663-668) and Komatsu et al. ( Nat. Commun. 2020, 11, 464). With our present calorimetric study on the transition from pure cubic ice to hexagonal ice we are able to clarify the value of the enthalpy change Δ H c→h to be -37.7 ± 2.3 J mol -1 . The transition temperature is identified as 226 K, much higher than in previous work on ice I sd . This is due to a catalytic effect of hexagonal faults on the transition, but even more importantly due to a relaxation exotherm that was not properly identified in the past.

We performed matrix-isolation infrared (MI-IR) spectroscopy of carbon dioxide monomers, CO 2 , and dimers, (CO 2 ) 2 , trapped in neon and in air. On the basis of vibration configuration interaction (VCI) calculations accounting for mode coupling and anharmonicity, we identify additional infrared-active bands in the MI-IR spectra due to the (CO 2 ) 2 dimer. These bands are satellite bands next to the established CO 2 monomer bands, which appear in the infrared window of Earth's atmosphere at around 4 and 15 μm. In a systematic carbon dioxide mixing ratio study using neon matrixes, we observe a significant fraction of the dimer at mixing ratios above 300 ppm, with a steep increase up to 1000 ppm. In neon matrix, the dimer increases the IR absorbance by about 15% at 400 ppm compared to the monomer absorbance alone. This suggests a high fraction of the (CO 2 ) 2 dimer in our matrix experiments. In atmospheric conditions, such increased absorbance would significantly amplify radiative forcings and, thus, the greenhouse warming. To enable a comparison of our laboratory experiment with various atmospheric conditions (Earth, Mars, Venus), we compute the thermodynamics of the dimerization accordingly. The dimerization is favored at low temperatures and/or high carbon dioxide partial pressures. Thus, we argue that matrix isolation does not trap the gas composition "as is". Instead, the gas is precooled to 40 K, where CO 2 dimerizes before being trapped in the matrix, already at very low carbon dioxide partial pressures. In the context of planetary atmospheres, our results improve understanding of the greenhouse effect for planets of rather thick CO 2 atmospheres such as Venus, where a significant fraction of the (CO 2 ) 2 dimer can be expected. There, the necessity of including the mid-IR absorption by stable (CO 2 ) 2 dimers in databases used for modeling radiative forcing, such as HITRAN, arises.

High-pressure ice polymorphs are important for our understanding of hydrogen bonding and exist in the interior of the earth and icy moons. Nonetheless, spectroscopic information about them is scarce, where no information about their optical properties in the near-infrared (NIR) region is available at all. We here report NIR spectra of six ice polymorphs differing in terms of their density and O-atom topology, namely, ices II, IV, V, VI, IX, and XII, in comparison with the known spectra of ice I h . By contrast to earlier work, we do not use mulling agents or transmission of thin films but use diffuse reflectance on powdered samples in liquid nitrogen. The first overtone of the OH-stretching mode is identified as the marker band most suitable to distinguish between these ices. There is a clear blue shift of this band that increases with increasing topological density in addition to a significant narrowing of the band.

We utilized fluorescence spectroscopy to learn about the molecular arrangement of naphthalene (Np) and 1-methylnaphthalene (MeNp) in frozen aqueous solutions. The freezing induces pronounced compound aggregation in the freeze-concentrated solution (FCS) in between the ice grains. The fluorescence spectroscopy revealed prevalent formation of a vitrified solution and minor crystallization of aromatic compounds. The FCS is shown as a specific environment, differing significantly from not only the pure compounds but also the ice surfaces. The results indicate marked disparity between the behavior of the Np and the MeNp; the cooling rate has a major impact on the former but not on the latter. The spectrum of the Np solution frozen at a faster cooling rate (ca 20 K/min) exhibited a temperature-dependent spectral behavior, whereas the spectrum of the solution frozen at a slower rate (ca 2 K/min) did not alter before melting. We interpret the observation through considering the varied composition of the FCS: Fast freezing leads to a higher water content expressed by the plasticizing effect, allowing molecular rearrangement, while slow cooling produces a more concentrated and drier environment. The experiments were conceived as generalizable for environmentally relevant pollutants and human-made freezing.

We present an analysis of ice nucleation kinetics from near-ambient pressure water as temperature decreases below the homogeneous limit T H by cooling micrometer-sized droplets (microdroplets) evaporatively at 10 3 -10 4 K/s and probing the structure ultrafast using femtosecond pulses from the Linac Coherent Light Source (LCLS) free-electron X-ray laser. Below 232 K, we observed a slower nucleation rate increase with decreasing temperature than anticipated from previous measurements, which we suggest is due to the rapid decrease in water's diffusivity. This is consistent with earlier findings that microdroplets do not crystallize at <227 K, but vitrify at cooling rates of 10 6 -10 7 K/s. We also hypothesize that the slower increase in the nucleation rate is connected with the proposed "fragile-to-strong" transition anomaly in water.

Calorimetric and optical cryo-microscope measurements of 10-64 wt % citric acid (CA) solutions subjected to moderate (3 K/min) and slow (0.5 and 0.1 K/min) cooling/warming rates and also to quenching/moderate warming between 320 and 133 K are presented. Depending on solution concentration and cooling rate, the obtained thermograms show one freezing event and from one to three liquid-glass transitions upon cooling and from one to six liquid-glass and reverse glass-liquid transitions, one or two freezing events, and one melting event upon warming of frozen/glassy CA/H2O. The multiple freezing events and glass transitions pertain to the mother CA/H2O solution itself and two freeze-concentrated solution regions, FCS1 and FCS2, of different concentrations. The FCS1 and FCS2 (or FCS22) are formed during the freezing of CA/H2O upon cooling and/or during the freezing upon warming of partly glassy or entirely glassy mother CA/H2O. The formation of two FCS1 and FCS22 regions during the freezing upon warming to our best knowledge has never been reported before. Using an optical cryo-microscope, we are able to observe the formation of a continuous ice framework (IF) and its morphology and reciprocal distribution of IF/(FCS1 + FCS2). Our results provide a new look at the freezing and glass transition behavior of aqueous solutions and can be used for the optimization of lyophilization and freezing of foods and biopharmaceutical formulations, among many other applications where freezing plays a crucial role.

Several proton-disordered crystalline ice structures are known to proton order at sufficiently low temperatures, provided that the right preparation procedure is used. For cubic ice, ice Ic, however, no proton ordering has been observed so far. Here, we subject ice Ic to an experimental protocol similar to that used to proton order hexagonal ice. In situ FT-IR spectroscopy carried out during this procedure reveals that the librational band of the spectrum narrows and acquires a structure that is observed neither in proton-disordered ice Ic nor in ice XI, the proton-ordered variant of hexagonal ice. On the basis of vibrational spectra computed for ice Ic and four of its proton-ordered variants using classical molecular dynamics and ab initio simulations, we conclude that the features of our experimental spectra are due to partial proton ordering, providing the first evidence of proton ordering in cubic ice. We further find that the proton-ordered structure with the lowest energy is ferroelectric, while the structure with the second lowest energy is weakly ferroelectric. Both structures fit the experimental spectral similarly well such that no unique assignment of proton order is possible based on our results.