Perturbation analysis of the υ = 6 level in the d3Δ state of CS based on its near-infrared absorption spectrum

The spectrum of CS was recorded in the region of 12,086-12,630 cm(-1) by employing optical heterodyne concentration modulation laser absorption spectroscopy. Nearly 350 transitions were assigned to the (6, 0) band in the d(3)Δ-a(3)Π system of CS. The overtone transitions of the (12, 0) band in the a(3)Π(2)-a(3)Π(0) transition were first observed due to the perturbation interaction between d(3)Δ(1) and a(3)Π(2). The Λ doubling in the a(3)Π(1) state was also resolved at high rotational levels. The molecular constants of the a(3)Π (υ = 0) and d(3)Δ (υ = 6) levels and the perturbation parameters of the d(3)Δ (υ = 6) level were determined through nonlinear least-squares fitting using effective hamiltonians. The calculations of mixing fractions of the perturbed states were performed in order to obtain precise information on the perturbations of the d(3)Δ (υ = 6) levels. The mechanisms for perturbations of d(3)Δ (υ = 6) with the a(3)Π (υ = 12) and A(1)Π (υ = 1) levels, especially for the second-order perturbation, were discussed and explained according to first-order nondegenerate perturbation theory.     

The pure rotational spectrum of the CrS radical in its X 5Π(r) state

The pure rotational spectrum of the CrS radical has been measured in its ground X (5)Π(r) state using gas-phase millimeter/submillimeter direct absorption methods. The molecule was created by the reaction of chromium vapor, sublimed in a Broida-type oven, with hydrogen sulfide. Eleven rotational transitions were recorded for this free radical in the frequency range of 280-405 GHz; in most transitions, all five spin components were observed, and lambda-doubling was resolved in the Ω=0, 1, and 2 ladders. The data were fit with a Hund's case (a) Hamiltonian and rotational, spin-orbit, spin-spin, and lambda-doubling constants were established. Higher order spin and spin-orbit terms were essential in the analysis. The lambda-doubling constants indicate a nearby (5)Σ(+) state at an energy of ～1500-2000?cm(-1). A bond length of 2.0781 A? was derived for CrS from the data, which is larger than the value of 2.0682 A? found for MnS by ～0.01?A?. In contrast, the bond distance for MnO is greater than that of CrO by 0.03 A?, an illustration of the subtle differences between 3d oxide and sulfides. CrS is the second molecule in a (5)Π state that has been studied by rotational spectroscopy.     

Three-quantum transition probabilities in the ν3 manifold of SF6 and the assignment of the observed 3ν3 transition in the i.r. spectrum

A theoretical expression has been derived for the intensity of a three-vibrational-quantum electric-dipole transition and has been used to calculate the intensities of the transitions from the ground state to the two F_1u components of 3ν₃ of SF₆. The calculated intensity of 1.02 × 10⁻² km/mol is in reasonable agreement with the observed intensity of 4.8 × 10⁻² km/mol.     

Radiation-chemical processes leading to origination and accumulation of oxygen in the Earth’s atmosphere

The role of natural radioactivity in the formation of the oxygen atmosphere of the Earth is discussed. The origination of oxygen in the free state in the hydrosphere and atmosphere is associated with the radiolysis of the water of the World ocean under the irradiation of radio active isotopes ⁴⁰K, ²³⁵U, ²³⁸U, and ²³²Th. The calculations showed that within the last 3.8 billion years the total weight of oxygen, which could be formed due to this process, is about 7.4?10¹⁷ kg, i.е., the value of the same order as the oxygen content in the modern atmosphere of the Earth. The Ocean was an intermediate collector and provided the nucleation of new forms of biological life with oxygen respiration. The consecutive transformation of the Earth’s atmosphere with a gradual increase in the oxygen content became the result of photosynthesis in algae and green plants and thus opened a way to the origination of complicated forms of the life.     

Discrete version of Wiener-Khinchin theorem for Chebyshev’s spectrum of electrochemical noise

A discrete version of Wiener-Khinchin theorem for Chebyshev’s spectrum of electrochemical noise is developed. Based on the discrete version of Wiener-Khinchin theorem, the theoretical discrete Chebyshev spectrum for the Markov random process is calculated. It is characterized by two parameters: the dispersion and the relaxation frequency (or relaxation time). The noise of corrosion process and the noise of recording equipment are measured. Using the theoretical Chebyshev spectrum, the Markov parameters were found both for the noise of the corrosion process and for the noise of the measuring equipment.     

Effect of the direction of the earth’s magnetic field lines on corrosive wear

In this work, the effect of the direction of the Earth’s magnetic field lines on the corrosive wear of steel samples in an aggressive medium was studied, and a study algorithm and a data processing algorithm were described.     

Analysis of the Rydberg structure in the vapor-phase electronic absorption spectrum of (η7-cycloheptatrienyl)(η5-cyclopentadienyl) chromium

Parameters of the Rydberg transitions in the vapor-phase absorption spectrum of (η⁷-C₇H₇)(η⁵-C₅H₅)Cr were analyzed in detail. A correspondence between the three Rydberg series in the short-wavelength region of the spectrum and low-frequency Rydberg bands was established. Vibronic structure of the observed transitions to the lowest Rydberg s, p _x,y , p _z , and d _xz,yz levels was interpreted. The long-wavelength and short-wavelength series, respectively characterized by quantum defect (σ) values of 1.26 and 0.82, were unambiguously assigned to the Rydberg p _x,y and d _xz,yz excitations, respectively. Transitions from the 3d _z 2 orbital to theR(n−1)f,Rnd _z 2, andRnp _z levels can contribute to the series characterized by a σ value of 1.04. The assignment was made of Rydberg bands in the spectral region corresponding to the principal quantum number (n) values of 5, 6, and 7 (in this region, interpretation of the spectral pattern is complicated because of the band shifts and broadening). Atn>5, changes in the σ values of the Rydberg excitations with increase in then value are due to configuration interaction. The electronic-excited states, which can be responsible for the observed changes in the Rydberg parameters, were determined. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1677–1684, September, 1999.     

The prospect of the dalton in the new SI: an educator’s point of view

If the definitions of the kilogram and the mole, based on exact values of the Planck and Avogadro constants, respectively, are accepted within the framework of the new SI, then the current definition of the dalton cannot be retained. Acceptance implies redefinition of the dalton exactly in terms of the kilogram. The redefined, exact dalton is useless in mass spectrometry, and hence, a new quantity for the carbon-12 reference mass would have to be established—against the principle of Ockham’s razor. In order to remove the roots of this awkward concept, the kilogram based on the Planck constant, and the mole, consisting of a particular number of entities equal to the inexactly determined numerical value of gram-to-dalton mass ratio, should be included in the new SI system. Some controversies related to the concept of mole have been also briefly outlined.     

Infrared spectra of triacetylene in the 4000-220 cm−1 region: Absolute band intensity and implications for the atmosphere of Titan

The gas phase infrared spectra of triacetylene were studied at room temperature in the 4000-220 cm⁻¹ wavenumber region. The absolute intensity of all the bands of noticeable strength were experimentally determined and the associated uncertainties were systematically estimated. The data obtained were then used for studying the detectability of C₆H₂ in Titan's atmosphere by means of infrared spectroscopy. The upper limit of mean stratospheric abundance derived from the already available Titan IR spectra (a fraction of ppb) is in agreement with the photochemical model estimates.     

Photostabilization of oxolinic acid in hydroxypropyl-β-cyclodextrins; implications for the effect of molecular self-assembly phenomena

Oxolinic acid (OXA) is a first-generation quinolone antibacterial agent, known to cause drug induced photosensitivity. In the present work its photoinduced degradation was monitored under simulated solar irradiation. The effect of photoprotecting agents on OXA stability was also assessed by drug complexation with hydroxypropyl-β-cyclodextrin (HPβCD). The complex was studied by UV-Vis and ¹H (2D) NMR Spectroscopy. A photostability indicating chromatographic method was developed and validated. Because OXA is insoluble in acidic solutions, and because an acidic solvent is necessary for successful chromatographic separation, a procedure was developed to pre-treat the sample. This method is suitable for the separation of degradation products from OXA and from each other. The method was also evaluated in the presence of HPβCD, in order to ensure that inclusion complexation did not generate inaccuracies. Investigation of OXA photodegradation profiles confirms first order kinetics and acceleration at higher initial sample concentrations. A 94% photostabilization upon complexation with HPβCD was achieved. Furthermore, molecular self association phenomena were determined by self titration experiments, using ¹H NMR Spectroscopy and suggestions were made for the photostabilization mechanism of cyclodextrins.     

The vibrational spectrum and the normal coordinate analysis of β-TiCl3

The vibrational spectrum of β-TiCl₃ is reported. The observed bands are assigned on the basis of the normal coordinate analysis by use of a valence force field. It was found that the A_2u mode is lower in frequency than that in α-TiCl₃ and one of the TiTi stretchings is 281 cm⁻¹, resulting in a TiTi stretching force constant of 81.6 N/m.     

Early impact of quantum physics on chemistry: George Hevesy’s work on rare earth elements and Michael Polanyi’s absorption theory

After Heitler and London published their pioneering work on the application of quantum mechanics to chemistry in 1927, it became an almost unquestioned dogma that chemistry would soon disappear as a discipline of its own rights. Reductionism felt victorious in the hope of analytically describing the chemical bond and the structure of molecules. The old quantum theory has already produced a widely applied model for the structure of atoms and the explanation of the periodic system. This paper will show two examples of the entry of quantum physics into more classical fields of chemistry: inorganic chemistry and physical chemistry. Due to their professional networking, George Hevesy and Michael Polanyi found their ways to Niels Bohr and Fritz London, respectively, to cooperate in solving together some problems of classical chemistry. Their works on rare earth elements and adsorption theory throws light to the application of quantum physics outside the reductionist areas. They support the heuristic and persuasive value of quantum thinking in the 1920–1930s. Looking at Polanyi’s later oeuvre, his experience with adsorption theory could be a starting point of his non-justificationist philosophy.     

Blue-shifted fluorescence spectrum in silica xerogels with incorporation of extract’s leaves

The spectral characteristics of different kind of leaves extracts fluorescence embedded in silica xerogel matrix under structural evolution promoted by heat treatment was studied. We obtain a higher PSII thermostability for extract of leaves, rich in chlorophyll such as spinach, made in darker condition than extract of leaves made in lighter (non-dark) conditions, both embedded in xerogel matrix, which remain bioactive over a very long period of time. In other kind of leaves such geranium, after chlorophyll decomposition the quenching center are formed at temperatures about 800 °C, whereas in buxus sempervirens leaves fluorescing aggregates remain in temperatures as high as 1,000 °C, when their are embedded in silica xerogel matrix. In general blue-shift fluorescence is observed in all cases indicating the PSII denaturizing and formation of fluorescing aggregates in relatively high temperatures.     

Rotational spectrum of SiC2 in the ν3 excited state

The rotational spectra of SiC₂ in the vibrationally excited states of the ring deformation mode (υ₃ = 1, 2) were observed in the frequency region of 140–400 GHz by using a source-modulated microwave spectrometer combined with a free space absorption cell. SiC₂ was produced in the cell by discharging a mixture of SiH₄, C₂H₂ and CO. Least-squares analysis of the observed spectral lines yielded the rotational constants and the centrifugal distortion constants precisely. Sextic, octic and decatic centrifugal distortion constants were required in the least-squares fit in order to get a good fit of the observed frequencies to those calculated within experimental errors. The inertial defects for the υ₃ = 1 state and the υ₃ = 2 state do not show a linear dependence on the vibrational quantum number. The quartic centrifugal distortion constants, Δ_JK, Δ_K and δ_K, are abnormally large, and show a large change on the vibrational states. These abnormal behaviours are interpreted in terms of a large amplitude motion of the ν₃ mode.     

Diode laser i.r. spectrum and rovibrational analysis of CF3Br in the ν2 + ν3 region

The gas phase i.r. spectrum of CF₃Br, with natural isotopic abundance, has been investigated in the ν₂+ ν₃ region near 1120 cm⁻¹ using a tunable diode laser spectrometer. The measurements have been carried out at low temperature (⋍ 200 K) to minimize the effects due to the “hot” band absorptions. The K structure of many P(J) and R(J) manifolds has been resolved and analyzed: the maximum J value reached for individual lines was 62 and 70 for CF₃⁷⁹Br and CF₃⁸¹Br, respectively. The identified transitions have been used in a least-squares fit to the energy expression up to the quartic terms and molecular parameters for the ν₂ + ν₃ combination have been obtained. Residual weak features due to “hot” bands of ν₃ and ν₆ have been assigned; the J structure has been analyzed by means of a polynomial procedure and spectroscopic constants for both the isotopomers have been derived.     

Molecular interpretation of Trouton’s and Hildebrand’s rules for the entropy of vaporization of a liquid

The entropy of vaporization at a liquid’s boiling point is well approximated by Trouton’s rule and even more accurately by Hildebrand’s rule. A cell method is used here to calculate the entropy of vaporization for a range of liquids by subtracting the entropy of the gas from that of the liquid. The liquid’s entropy is calculated from the force magnitudes measured in a molecular dynamics simulation based on the harmonic approximation. The change in rotational entropy is not accounted for except in the case of liquid water. The predicted entropies of vaporization agree well with experiment and Trouton’s and Hildebrand’s rules for most liquids and for water except other liquids with hydrogen bonds. This supports the idea that molecular rotation is close to ideal at a liquid’s boiling point if hydrogen bonds are absent; if they are present, then the rotational entropy gain must be included. The method provides a molecular interpretation of those rules by providing an equation in terms of a molecule’s free volume in a liquid which depends on the force magnitudes. Free volumes at each liquid’s boiling point are calculated to be ～1 Å³ for liquids lacking hydrogen bonds, lower at ～0.3 Å³ for those with hydrogen bonds, and they decrease weakly with increasing molecular size.     

The Importance of Nutraceuticals in COVID-19: What’s the Role of Resveratrol?

Since COVID-19 has affected global public health, there has been an urgency to find a solution to limit both the number of infections, and the aggressiveness of the disease once infected. The main characteristic of this infection is represented by a strong alteration of the immune system which, day by day, increases the risk of mortality, and can lead to a multiorgan dysfunction. Because nutritional profile can influence patient’s immunity, we focus our interest on resveratrol, a polyphenolic compound known for its immunomodulating and anti-inflammatory properties. We reviewed all the information concerning the different roles of resveratrol in COVID-19 pathophysiology using PubMed and Scopus as the main databases. Interestingly, we find out that resveratrol may exert its role through different mechanisms. In fact, it has antiviral activity inhibiting virus entrance in cells and viral replication. Resveratrol also improves autophagy and decreases pro-inflammatory agents expression acting as an anti-inflammatory agent. It regulates immune cell response and pro-inflammatory cytokines and prevents the onset of thrombotic events that usually occur in COVID-19 patients. Since resveratrol acts through different mechanisms, the effect could be enhanced, making a totally natural agent particularly effective as an adjuvant in anti COVID-19 therapy.     

The contribution of gas chromatography to the resynthesis of the post-Byzantine artist’s technique

Gas chromatographic analysis of ethyl chloroformate derivatives of samples taken from the paint layers of post-Byzantine panel paintings permitted the successful characterisation of the different binding media used in them. This paper describes an analytical study of various post-Byzantine binding media such as egg yolk and egg/oil emulsion, using gas chromatography. The characterisation of these icons’ binding media is an important task, as it contributes to our understanding of and the reconstruction of the post-Byzantine artists’ palette. It also enables us to investigate the validity of our assumptions about the influences of Venetian style on Greek icon painting techniques from the sixteenth to the early nineteenth century, which up to now have been based on information in artists’ handbooks. The methodology involves two experimental steps: (1) hydrolysis of the proteins and triglycerides in the binding media to obtain free amino acids and fatty acids, and (2) the formation of ethyl chloroformate derivatives via derivatization with ethyl chloroformate (ECF). This methodology is of considerable interest, since it permits the identifcation of the nature of the proteinaceous binders used in these works through the simultaneous derivatization and determination of amino acids and fatty acids. Advantages of this methodology include the small quantity of sample required and the minimum preparation time involved. The proteinaceous media can be determined based on the ratios of seven stable amino acids, while the type of emulsions and drying oils used can be determined from the fatty acid ratio. Electronic supplementary material Supplementary material is available in the online version of this article at and is accessible for authorized users.     

Development of a gas chromatography — mass spectrometry method for the determination of carbon disulfide in the atmosphere

Carbon disulfide (CS₂), a relevant reduced sulfur compound in air, is well-known for its malodor and its significant effect on global atmospheric chemistry. Therefore, a reliable method for determining CS₂ in atmospheric samples has been developed based on solid-phase sampling and gas chromatography–mass spectrometry (GC–MS). Two types of solid-phase sampling supports (Orbo-32 and SKC) and the elution with organic solvents — hexane and toluene — were evaluated for low-volume outdoor sampling. Recovery studies and the standard addition method were carried out to demonstrate the proper determination of CS₂ in the absence of the influence of interferences such as ozone, hydrogen sulfide or water — important atmospheric pollutants —. The proposed methodology was validated by performing experiments in a high-volume smog chamber and by comparison with two reference optical methods, Fourier Transform Infrared (FTIR) and Differential Optical Absorption Spectroscopy (DOAS) installed in these facilities. Satisfactory analytical parameters were reported: fast analysis, a correct repeatability of 6 ± 1% and reproducibility of 14 ± 3%, and low detection limits of 0.3–0.9 pg m^? 3. Finally, the method was successfully applied to industrial samples near a pulp factory area, where a high correlation between industrial emissions and reported carbon disulfide concentrations were observed.