Multiplet States Research Articles

4f electron temperature driven ultrafast electron localization

Valence transitions in strongly correlated electron systems are caused by orbital hybridization and Coulomb interactions between localized and delocalized electrons. The transition can be triggered by changes in the electronic structure and is sensitive to temperature variations, applications of magnetic fields, and physical or chemical pressure. Launching the transition by photoelectric fields can directly excite the electronic states and thus provides an ideal platform to study the correlation among electrons on ultrafast timescales. The EuNi2(Si0.21Ge0.79)2 mixed-valence metal is an ideal material to investigate the valence transition of the Eu ions via the amplified orbital hybridization by the photoelectric field on subpicosecond timescales. A direct view on the 4f electron occupancy of the Eu ions is required to understand the microscopic origin of the transition. Here we probe the 4f electron states of EuNi2(Si0.21Ge0.79)2 at the sub-ps timescale after photoexcitation by x-ray absorption spectroscopy across the Eu M5-absorption edge. The observed spectral changes due to the excitation indicate a population change of total angular momentum multiplet states J = 0, 1, 2, and 3 of Eu3+ and the Eu2+ J = 7/2 multiplet state caused by an increase in 4f electron temperature that results in a 4f localization process. This electronic temperature increases combined with fluence-dependent screening accounts for the strongly nonlinear effective valence change. The data allow us to extract a time-dependent determination of an effective temperature of the 4f shell, which is also of great relevance in the understanding of metallic systems' properties, such as the ultrafast demagnetization of ferromagnetic rare-earth intermetallic and their all-optical magnetization switching. In addition, our results elucidate the energetics of charge fluctuations in valence-mixed electronic systems, which provide enriched knowledge regarding the role of valence transitions and orbital hybridization for quantum critical phenomena. Published by the American Physical Society 2024

Molecular Oxygen Trimer: Multiplet Structures and Stability.

We present a detailed theoretical study of the molecular oxygen trimer where the potential energy surfaces of the seven multiplet states have been calculated by means of a pair approximation with very accurate dimer ab initio potentials. In order to obtain all the states a matrix representation of the potential using the uncoupled spin representation has been applied. The and states are nearly degenerate and low-lying isomers appear for most multiplicities. A crucial point in deciding the relative stabilities is the zero-point energy which represents a sizable fraction of the electronic well-depth. Therefore, we have performed accurate diffusion Monte Carlo studies of the lowest state in each multiplicity. Analysis of the wavefunction allows a deeper interpretation of the cluster structures, finding that they are significantly floppy in most cases.

Wigner-molecularization-enabled dynamic nuclear polarization

Multielectron semiconductor quantum dots (QDs) provide a novel platform to study the Coulomb interaction-driven, spatially localized electron states of Wigner molecules (WMs). Although Wigner-molecularization has been confirmed by real-space imaging and coherent spectroscopy, the open system dynamics of the strongly correlated states with the environment are not yet well understood. Here, we demonstrate efficient control of spin transfer between an artificial three-electron WM and the nuclear environment in a GaAs double QD. A Landau–Zener sweep-based polarization sequence and low-lying anticrossings of spin multiplet states enabled by Wigner-molecularization are utilized. Combined with coherent control of spin states, we achieve control of magnitude, polarity, and site dependence of the nuclear field. We demonstrate that the same level of control cannot be achieved in the non-interacting regime. Thus, we confirm the spin structure of a WM, paving the way for active control of correlated electron states for application in mesoscopic environment engineering.

大気安定な発光性ポリクロロトリアリールメチルラジカルの開発と機能創出

Stable radicals possess open-shell electronic states and exhibit vivid physical properties such as electrical conductivity and magnetism attributed to unpaired electrons. Their luminescence properties, however, have yet to be well examined, mainly due to the rarity of emissive radicals and chemical reactivity in their excited states. I have developed highly-photostable luminescent organic radicals and luminescent open-shell metal complexes with luminescent radicals as ligands, and investigated photofunctions based on their doublet or multiplet states. The studies suggest that the radicals can demonstrate photofunctions unique to their open-shell electronic states, such as magnetic-field-controlled luminescence, which are unexpected or impossible to achieve for conventional closed-shell molecules. Such functions will expand the scope of the radicals in molecular photonics.

Computational tools for the simulation and analysis of spin-polarized EPR spectra

The EPR spectra of paramagnetic species induced by photoexcitation typically exhibit enhanced absorptive and emissive features resulting from sublevel populations that differ from thermal equilibrium. The populations and the resulting spin polarization of the spectra are dictated by the selectivity of the photophysical process generating the observed state. Simulation of the spin-polarized EPR spectra is crucial in the characterization of both the dynamics of formation of the photoexcited state as well as its electronic and structural properties. EasySpin, the simulation toolbox for EPR spectroscopy, now includes extended support for the simulation of the EPR spectra of spin-polarized states of arbitrary spin multiplicity and formed by a variety of different mechanisms, including photoexcited triplet states populated by intersystem crossing, charge recombination or spin polarization transfer, spin-correlated radical pairs created by photoinduced electron transfer, triplet pairs formed by singlet fission and multiplet states arising from photoexcitation in systems containing chromophores and stable radicals. In this paper, we highlight EasySpin’s capabilities for the simulation of spin-polarized EPR spectra on the basis of illustrative examples from the literature in a variety of fields ranging across chemistry, biology, material science and quantum information science.

Final ion charge spectra upon cascade decay of inner-shell vacancies in atomic Au

Final ion charge spectra produced by the cascade de-excitations of 1s- to 5p 3/2-vacancies of the gold atom are calculated by direct construction and analysis of the cascade decay trees. The energies of multivacancy configurations arising in the course of the cascade development, and the partial widths of radiation and radiationless cascade transitions are calculated using the Pauli–Fock approximation. The energies of the cascade transitions are calculated as the differences of total Pauli–Fock energies of initial and final ionic configurations which allowed excluding energy-forbidden radiationless transitions in numerous multivacancy configurations. Partial widths of transitions are expressed in the form that allowed accounting for the effect of electron subshell populations on the transition widths. The partial widths of the transitions between the states of the overlapping initial and final state multiplets are corrected so as to exclude energy-forbidden transitions between the multiplet states. It is demonstrated that accurate accounting for possible forbiddance of transitions between cascade configurations and the exclusion of energy-forbidden term-to-term transitions between the multiplets’ states are crucial in deep-initial-vacancy cascade simulations.

Testing the predictive power of realistic shell model calculations via lifetime measurement of the 11/2+ state in Sb131

The lifetime of the $11/{2}_{1}^{+}$ state in the $^{131}\mathrm{Sb}$ nucleus was measured at the LOHENGRIN spectrometer of the Institut Laue-Langevin via neutron-induced fission of $^{235}\mathrm{U}$ using $\ensuremath{\gamma}$-ray fast-timing techniques. The obtained value of ${T}_{1/2}=3\phantom{\rule{0.16em}{0ex}}$(2) ps, at the edge of the sensitivity of the experimental method, is the first result for the $11/{2}_{1}^{+}$ state half-life in neutron-rich Sb isotopes. The corresponding quadrupole reduced transition probability to the ground state is $B(E2)=1.{4}_{\ensuremath{-}0.6}^{+1.5}$W.u., indicating a noncollective nature of this state. Realistic shell-model calculations performed in a large valence space reproduce well the experimental value and point to a dominant ${2}^{+}(^{130}\mathrm{Sn})\ensuremath{\bigotimes}\ensuremath{\pi}{\mathrm{g}}_{7/2}$ configuration for the $11/{2}_{1}^{+}$ state, as expected in a weak-coupling scenario. At the same time, the sum of the quadrupole strength of the multiplet states is predicted to exceed the one of the $^{130}\mathrm{Sn}$ core as a consequence of the equal contribution of the proton and the proton-neutron quadrupole matrix elements, pointing to possible development of collectivity already in the close neighborhood of $^{132}\mathrm{Sn}$.

Electronic and magnetic properties of the topological semimetal SmMg2Bi2

Dirac semimetals show nontrivial physical properties and can host exotic quantum states like Weyl semimetals and topological insulators under suitable external conditions. Here, by combining angle-resolved photoemission spectroscopy measurements (ARPES) and first-principle calculations, we demonstrate that the Zintl-phase compound ${\mathrm{SmMg}}_{2}{\mathrm{Bi}}_{2}$ is in close proximity to a topological Dirac semimetallic state. ARPES results show a Dirac-like band crossing at the zone center near the Fermi level (${E}_{\mathrm{F}}$), which is further confirmed by first-principle calculations. Theoretical studies also reveal that ${\mathrm{SmMg}}_{2}{\mathrm{Bi}}_{2}$ belongs to a ${Z}_{2}$ topological class and hosts spin-polarized states around the ${E}_{\mathrm{F}}$. Zintl's theory predicts that the valence state of Sm in this material should be ${\mathrm{Sm}}^{2+}$, however, we detect many Sm-$4f$ multiplet states (flat-bands) whose energy positions and relative intensities suggest the presence of both dominant ${\mathrm{Sm}}^{2+}$ and minor ${\mathrm{Sm}}^{3+}$. The small concentration (2.5%) of ${\mathrm{Sm}}^{3+}$ in the bulk of a crystal is inferred to arise from Sm vacancies in the crystal. It is also evident that these flat bands and other dispersive states are strongly hybridized when they cross each other. Due to the presence of ${\mathrm{Sm}}^{3+}$ ions, the temperature dependence of the magnetic susceptibility $\ensuremath{\chi}(T)$ shows a Curie-Weiss-like contribution in the low-temperature region, in addition to the Van Vleck-like behavior expected for the ${\mathrm{Sm}}^{2+}$ ions. The present study will help to better understand the electronic structure, magnetism, and transport properties of related materials.

Does Cr3+ Occupy Tetrahedral Sites and Luminesce in Oxides? A First-Principles Exploration.

The Cr3+ activators have been adopted to produce desired near-infrared broadband emission via ligand field engineering by choosing hosts with appropriate sites. First-principles calculations help to analyze the site, valence, and luminescent mechanism of the activators. Our calculations on Mg2Al4Si5O18:Cr elucidate that the activators are dominated by Cr3+ at tetrahedral Al and octahedral Mg sites, while the experimentally reported near-infrared emission previously assigned to tetrahedral sites is actually produced by Cr3+ at the octahedral site. Meanwhile, our results show that the emission energies of Cr3+ activators at octahedral sites can be well predicted. Moreover, further calculations show that the quenching of the 4T2 → 4T1 transition of Cr3+ at a tetrahedral site is general due to nonradiative relaxation pathways mediated by sublevels split off from the 4T1 multiplet states by intrinsic or Jahn-Teller distortions. Our work shows that the sophisticated first-principles calculations put together here can be effective in exploring Cr3+ and potentially more general activators in crystals, which benefit the design and optimization of luminescent materials.

Effect of Ceramic Formation on the Emission of Eu3+ and Nd3+ Ions in Double Perovskites.

Herein, the structure, morphology, as well as optical properties of the powder and ceramic samples of Ba2MgWO6 are presented. Powder samples were obtained by high temperature solid-state reaction, while, for the ceramics, the SPS technique under 50-MPa pressure was applied. The morphology of the investigated samples showed some agglomeration and grains with a submicron size of 490–492 µm. The theoretical density and relative density of ceramics were calculated using the Archimedes method. The influence of sample preparation on the position, shape, and character of the host, as well as dopants emission was investigated. Sample sintering enhances regular emission of WO6 groups causing a blue shift of Ba2MgWO6 emission. Nonetheless, under X-ray excitation, only the green emission of inversion WO6 group was detected. For the ceramic doped with Eu3+ ions, the emission of both host and dopant was detected. However, for the powder efficient host to activator energy, the transfer process occurred, and only the magnetic dipole emission of Eu3+ was detected. The intensity of Nd3+ ions of Ba2MgWO6 powder sample is five times higher than for the ceramic. The sintering process reduces inversion defects and creates a highly symmetrical site of neodymium ions. The emission of Ba2MgWO6:Nd3+ consists of transitions from the 4F3/2 excited level to the 4IJ multiplet states with the dominance of the 4F3/2→4I11/2 one. The spectroscopic quality parameter and branching ratio of Nd3+ emission are presented.

New emerging magnetic, optical and photocatalytic properties of Tb doped TiO2 interfaced with CoFe2O4 nanoparticles

The CoFe2O4/TiO2:Tb composite nanoparticles were prepared by a two-stage chemical route. The composites were characterized by using X-Ray Diffraction, Transmission Electron Microscopy, X-ray and UV Photoelectron Spectroscopies, FT-IR, Raman and UV–Vis spectroscopies.There is a polarized spin transfer at the interface between the cobalt ferrite into the TiO2 conduction band. As a result, the magnetic moments of oxygen vacancies in TiO2 becomes (ferro) magnetically ordered. The magnetic moments sublattice of Tb ions may have an either “ferro” or “antifero” coupling depending on the dopant concentration. The magnetic semiconductor intensifies the optical absorption in the visible. There is a band-to-band absorption assisted by single-occupied oxygen vacancies coupled to some local crystal lattice relaxations.The lifetime of the photoexcited electrons in the conduction band increases due to their coupling with magnetically ordered interface transferred states. Also, the trapping of electrons into multiplet states of Tb3+ reduces the recombination rate. The photocatalytic efficiency of the magnetically ordered titania increases with respect to bare TiO2. The reactive oxygen species produced at the solid–liquid interface of TiO2 were identified by Electron Spin Resonance coupled with spin-trapping technique. The results were correlated to the presence of the magnetic order inside the titania.

Cross-shell excitations in doubly magic 132Sn and its nearest neighbours

Large-scale shell-model calculations have been performed to study the excitation spectra of 132Sn and its nearest neighbours with a new cross-shell interaction constructed from two widely used interactions, sn100pn and CWG, of this mass region. A few of the two-body matrix elements have been tuned to reproduce the low-lying multiplet states of 132Sn. The energy spectra and the transition probabilities of 132Sn have been calculated within an extended space. The results reproduce even the most recent data. The excitation spectra for other nearest neighbours and the transition probabilities related to core-excited states are reproduced reasonably well. However, calculated E1 transition probabilities are under-predicted in most cases.

Rotational dynamics of O2 in the electronic ground XΣg−3 state induced by an intense femtosecond laser field

We theoretically and numerically investigate rotational dynamics of ${\mathrm{O}}_{2}$ in the electronic $X^{3}\mathrm{\ensuremath{\Sigma}}_{g}^{\ensuremath{-}}$ ground state induced by an intense femtosecond laser field. The rotational dynamics are calculated by two different models. One of the models includes triplet splittings explicitly in rotational energy levels originated from an electronic spin (a spin-dependent model), and the other omits the triplet splittings (a spin-independent model). We find that the final rotational population after the interaction with the laser field does not depend on the models. On the other hand, we find that the rotational dynamics evaluated by alignment degrees and angular distributions of molecular axes depend on the models. Although the rotational dynamics calculated by the spin-independent model is similar to that calculated by the spin-dependent model within 5 ps, the triplet splittings in the rotational energy levels affect the rotational dynamics after 5 ps. This is explained by the inverse of the energy difference between triplet splittings in the rotational levels. We show that the multiplet energy splittings in rotational energies should be included when the rotational dynamics in the multiplet electronic state are considered. We also investigate excitation processes on the basis of time evolutions of state populations and find that there are excitation pathways with double as well as single bifurcations depending on the initial state.

Selective Orbital Imaging of Excited States with X-Ray Spectroscopy: The Example of α -MnS

Herein we show that non-resonant inelastic x-ray scattering involving an $s$ core level is a powerful spectroscopic method to characterize the excited states of transition metal compounds. The spherical charge distribution of the $s$ core hole allows the orientational dependence of the intensities of the various spectral features to produce a spatial charge image of the associated multiplet states in a straightforward manner, thereby facilitating the identification of their orbital character. In addition, the $s$ core hole does not add an extra orbital angular momentum component to the multiplet structure so that the well-established Sugano-Tanabe-Kamimura diagrams can be used for the analysis of the spectra. For $\alpha$-MnS we observe the spherical charge density corresponding to its high spin $3d^5$ ($^6A_1$) ground state configuration and we were able to selectively image its excited states and identify them as $t_{2g}$ ($^5T_2$) and $e_g$ ($^5E$) with an energy splitting $10Dq$ of 0.78\,eV.

Spectroscopic properties of open shell diatomic molecules using Piris natural orbital functionals.

Spectroscopic properties such as equilibrium distances, vibrational constants, rotational constants, dissociation energies, and excitation energies are calculated for nine heteronuclear diatomic molecules (PH, NF, NH, NO, CS, AlF, ClF, BeO and CF) using an interactive pair model (PNOF7s), that has been generalized for spin multiplet states, and its second order perturbation variant, NOF-MP2, which was also generalized for multiplets. The results obtained are compared with Complete Active Space (CASSCF) and Complete Active Space Perturbation Theory (CASPT2). It is shown that the potential energy curves provided by the PNOF functional for open shell diatomic molecules are in acceptable agreement with those from CASSCF and CASPT2. The spectroscopic constants depending at most on the second derivative of the potential energy are in good agreement with experiment, while those requiring the evaluation of the third and fourth derivatives show larger deviations from experiment and from those predicted by CASPT2. Thus, it is shown that the PNOF functional extension to multiplets is an alternative approach in predicting spectroscopic constants of molecules where static correlation plays an important role, like the open shell heteronuclear diatomic molecules studied in this work.

(Luminescence and Display Materials Division Centennial Outstanding Achievement Award Address) Investigation of Luminescent Materials based on First-principles Calculations of Multiplet States

The transitions between multiplet states of rare-earth (RE) and transition-metal (TM) ions in crystals are utilized in variety of luminescent materials. Therefore, for the theoretical design of novel luminescent materials, a deep understanding of multiplet states and a nonempirical prediction of multiplet spectra are indispensable. For these purposes, a configuration interaction calculation program based on the discrete-variational Xa (DV-Xa) molecular orbital method [1] was developed, which is known as the discrete-variational multi-electron (DVME) program [2]. There is also a relativistic version of the DVME program [3] based on the relativistic DV-Xa method [4], which is especially useful for the analysis of RE-doped luminescent materials [5] since both the relativistic effects and the many-electron effects can be considered simultaneously without any empirical parameters. The DVME calculations have been applied to analyze various luminescent materials such as ruby [2], Mn4+-doped fluorides [6] and RE-doped LiYF4 [5]. Various types of multiplet spectra originating from d-d, f-f, f-d, and charge transfer (CT) [7, 8] transitions have been reproduced without any empirical parameters and the origins of the spectral peaks have been elucidated based on the configuration analysis of the explicitly obtained many-electron wave functions. In addition, relationships between the multiplet energy and the local structure of TM ions in crystals have been investigated in detail by creating various energy-structure maps based on systematic DVME calculations. The systematic data obtained by first-principles calculations can be also used as the training data for machine learning to create a simple predictive model. In this lecture, some representative results of the investigation of luminescent materials based on first-principles calculations of multiplet states using the DVME program will be presented.[1] H. Adachi, M. Tsukada, and C. Satoko, J. Phys. Soc. Jpn., 45, 875 (1978).[2] K. Ogasawara T. Ishii, I. Tanaka, and H. Adachi, Phys. Rev. B, 61 143 (2000).[3] K. Ogasawara, T. Iwata, Y. Koyama, and T. Ishii, I. Tanaka, and H. Adachi, Phys. Rev. B, 64, 115413 (2001).[4] A. Rosén, D.E. Ellis, H. Adachi, and F.W. Averill, J. Chem. Phys., 65, 3629 (1976).[5] K. Ogasawara, S. Watanabe, H. Toyoshima, M.G. Brik, Handbook on Physics and Chemistry of Rare Earths, 37, 1 (2007).[6] M. Novita, T. Honma, B. Hong, A. Ohishi, K. Ogasawara, J. Lumin. 169, 596 (2016).[7] S. Takemura, K. Ogasawara, Opt. Mater.: X, 1, 100005 (2019).[8] S. Takemura, K. Ogasawara, J. Lumin. 214, 116542 (2019).

Multiple Sequential Ionization of Valence n = 4 Shell of Krypton by Intense Femtosecond XUV Pulses

Sequential photoionization of krypton by intense extreme ultraviolet femtosecond pulses is studied theoretically for the photon energies below the 3d excitation threshold. This regime with energetically forbidden Auger decay is characterized by special features, such as time scaling of the level population. The model is based on the solution of rate equations with photoionization cross sections of krypton in different charge and multiplet states determined using R-matrix calculations. Predictions of the ion yields and photoelectron spectra for various photon fluence are presented and discussed.

Ab initio calculation of the electron capture spectrum of 163Ho: Auger–Meitner decay into continuum states

Determining the electron neutrino mass by electron capture in 163Ho relies on an accurate understanding of the differential electron capture nuclear decay rate as a function of the distribution of the total decay energy between the neutrino and electronic excitations. The resulting spectrum is dominated by resonances due to local atomic multiplet states with core holes. Coulomb scattering between electrons couples the discrete atomic states, via Auger–Meitner decay, to final states with free electrons. The atomic multiplets are above the auto-ionisation energy, such that the delta functions representing these discrete levels turn into a superposition of Lorentzian, Mahan- and Fano-like line-shapes. We present an ab initio method to calculate nuclear decay modifications due to such processes. It includes states with multiple correlated holes in local atomic orbitals interacting with unbound Auger–Meitner electrons. A strong energy-dependent, asymmetric broadening of the resonances in good agreement with recent experiments is found. We present a detailed analysis of the mechanisms determining the final spectral line-shape and discuss both the Fano interference between different resonances, as well as the energy dependence of the Auger–Meitner Coulomb matrix elements. The latter mechanism is shown to be the dominant channel responsible for the asymmetric line-shape of the resonances in the electron capture spectrum of 163Ho.

Effect of R substitution in spin glass RFeTi2O7 compounds

Zirconolite oxides R3+Fe3+Ti2O7 (R rare earth element) are known to exhibit spin glass behaviour at low temperatures. Here we present a detailed study of these compounds for R = Eu, Gd, Dy, Ho, and Er, together with reviewed previous measurements on Sm, Tb, Tm, Yb and Lu, with the scope of determining the role played by the rare earth on their magnetic properties. They have been investigated using X-ray powder diffraction, and further characterized by magnetization, frequency dependent ac susceptibility and heat capacity measurements. RFeTi2O7 compounds are all isostructural showing orthorhombic structure, space group Pcnb at 300 K. Disorder of the magnetic ions in the RFeTi2O7 lattice induces spin glass behaviour at low temperatures, mainly due to the Fe sublattice. We show that magnetic rare earth ions participate in the spin glass state tuning its properties. The single ion anisotropy of the R3+ ions, excluding exchange interaction with other magnetic ions, has been calculated by ab initio methods, and expressed in terms of the g tensor of the ground doublet or quasi-doublet in Kramers (Sm, Dy, Er, Yb) and non-Kramers (Tb, Ho) ions, respectively, in an effective spin S* = 1/2 model. In the case of R with a singlet ground state (Eu, Tm) or a multiplet state (Gd), the ion is isotropic. We show that the relative increase in the spin-glass temperature ΔTSGR/TSGFe with respect to the LuFeTi2O7, where Lu is non-magnetic, correlates qualitatively with the product of the ratio gz/gJ (R = Tb, Dy, Ho, and Er), or g⊥/gJ (R = Sm), times the ratio of exchange interactions J~R,FeJFe,Fe determined from the paramagnetic room temperature susceptibility measurements. Besides, for increasing anisotropy the spin glass transition dynamics slows down to values typical of cluster glass. The coercive field below the transition is increased in the same trend. This paper explains the effect of the R-Fe exchange interaction and R single ion anisotropy on the spin-glass behaviour of these compounds.

DFT исследование элементарных актов сверхкритического водного окисления на примере каталитической реакции радикальной диссоциации воды с участием модельного кластера Fe4O6

This report details aspects of the reactivity of the products of catalytic dissociation of water as applied to the description of the nature of supercritical water oxidation and other oxidative SCF processes in general. It has been shown quantum chemically that the products of thermodynamically nonequilibrium to one degree or another dissociation of water on the surface of a model Fe4O6 cluster of different multiplet nature can act as effective agents for interaction with atmospheric oxygen and organic compounds. The antiferromagnetic forms of iron oxides can actively participate in radical reactions. It is shown using a model cluster Fe4O6 as an example. The radical reactions are able to easily change their multiplet state by simple chemisorption of 3O2 on their surface. In combination with the ability of water to dissociate on the model Fe4O6 cluster by the ionic type, the latter can easily transform into a triplet system, which, accordingly, leads to the emergence of an equilibrium biradical water dissociation formally even at room temperature. Hydrate-oxygen interactions on the surface of the Fe4O6 cluster lead to the generation of either an extremely reactive iron-hydroperoxide complex or a hydroperoxyl radical capable of conducting oxidative processes under SCF conditions in the volume of the corresponding fluid. It is shown the dissociative chemisorption of a water molecule on a Fe4O6 cluster in a triplet state (initiated, for example, by chemisorption of 3O2), in contrast to the heterolytic dissociation of water (whose thermodynamic equilibrium is shifted towards the molecular form of water), is practically a thermodynamically equilibrium process. It is this fact allowed us to consider the hydride-hydroxyl form of the Fe4O6 triplet cluster as one of the real agents for the oxidation of propylene glycol by the example of its first stage of catalytic dehydrogenation.