Isotopic Molecules Research Articles

Simultaneous measurement of 13C-,18O-, and 17O- isotopes of CO2 using a compact mid-infrared hollow waveguide gas sensor

A compact gas sensor has been developed for the first time employing a quantum cascade laser (QCL) with a central wavelength of 4.32 μm, combined with direct absorption spectroscopy technology and a hollow waveguide. The sensor could measure the concentrations of four isotopic molecules (16O12C16O, 18O12C16O, 16O13C16O, and 17O12C16O) in CO2 gas simultaneously, thereby obtaining the relative isotope ratios of δ13C, δ18O, and δ17O. By adjusting the incident light path, the anomalous absorption peaks in the system have been effectively suppressed, and a compact feedback function generator has been integrated to ensure control of the laser output wavelength to eliminate the loss of measurement precision caused by wavelength fluctuations. Under the two conditions of free-running and wavelength-controlled, a standard CO2 sample with a concentration of 5 % was measured continuously. The results showed that under wavelength-controlled conditions, the precision of the four isotopic molecule concentration measurements was improved by a minimum of 1.8 times, and the measurement precision could be further improved after filtering. According to the Allan variance analysis, the detection precision for δ13C, δ18O, and δ17O were 0.7 ‰, 0.62 ‰, and 1.58 ‰, respectively, at the optimal integration time of 98 seconds. This study has the potential for respiratory diagnosis to detect simultaneously the values of δ13C, δ18O, and δ17O in exhaled samples.

Computational investigation of isotopic effect in H2@X12N12 and H2O@X12N12 (X = B and Al) molecules

In this work, we reported isotopic effect in H2@X12N12 and H2O@X12N12 (X = B and Al) molecules at LC-ωPBE/6-311 G(d,p) level of theory. Zero-point energies values (ZPEs) of H2, H2O, H2@X12N12 and H2O@X12N12 molecules were calculated. Isotopes influenced the excess energies attained by molecules due to compression. The changes in ZPE of H2@X12N12 and H2O@X12N12 and those isotopic molecules intensely surpass those of the H2 and H2O molecules, subsequent in the great deuterium and tritium isotope effects. The excess of compression energy (Δ ɛ) obtained by the molecule under compression was sensibly, about 5.00–2.60 (X = B) and 1.48–2.63 (X = Al) kcal/mol. Larger kH/kD and kH/kT values were found in the presence of X = B than X = Al. These outcomes were recommended as a probe for analysis molecular compression of enzymatic positions; they may be significant for exploring extremely great experimental isotope effects in various enzymatic reactions, where they were ascribed to the tunneling.

Experimental determinations of carbon and hydrogen isotope fractionations and methane clumped isotope compositions associated with ethane pyrolysis from 550 to 600 °C

Methane clumped isotope compositions signify the relative natural abundances of rare, doubly substituted isotopic species of methane (13CH3D and 12CH2D2) and have emerged as a new isotopic tool to trace the sources, sinks, and lifecycles of methane in the environment. Such measurements can identify equilibration (or re-equilibration) temperatures if found to be in isotopic equilibrium or non-equilibrium processes (e.g., kinetically controlled reactions or mixing) if not in isotopic equilibrium. Naturally occurring thermogenic methane—formed by the thermally activated breakdown of larger organic molecules—has been found to have clumped isotope compositions consistent with equilibrium at reasonable gas formation temperatures in some settings and non-equilibrium processes occurring during either formation, migration, storage, or extraction in others. To explore the potential controls on the isotopic composition of thermogenic methane, we conducted isothermal time-series ethane pyrolysis experiments at 550 and 600 °C to measure methane and ethane 13C/12C and D/H fractionations and methane clumped isotope compositions (resolved 13CH3D and 12CH2D2). We explore the effects of modifying the initial clumped isotope composition of ethane and the addition of water vapor to pyrolysis experiments. We observe that ethane and methane 13C/12C are controlled by kinetic isotope effects and Rayleigh distillation processes. In contrast, ethane and methane D/H and methane clumped isotope compositions appear to be controlled by a combination of these processes and hydrogen isotope exchange. The hydrogen isotope exchange processes lead to isotopic equilibrium as reaction completion is approached for both D/H (ethane/methane) and methane clumped isotope compositions. We develop a chemical model based on a mass balance approach that accounts for inheritance vs. hydrogen-abstraction formation pathways for singly and doubly substituted isotopologues of ethane and methane that is compared to the experimental data. The model allows the determination of carbon and hydrogen kinetic isotope effects associated with ethane cracking and hydrogen abstraction reactions that, where applicable, we compare to prior theoretical constraints. From the comparison of the model to the experimental data, we infer that the kinetically controlled ethane and methane bulk isotope compositions and methane clumped isotope compositions are controlled by kinetic isotope effects (both primary and secondary) associated with both CC bond and CH bond cleavage reactions. Specifically, the methane clumped isotope compositions likely result from a combination of clumped isotope effects associated with ethane breakdown and/or assembly of methane isotopologues (expressed in terms of γ-factor parameters ≠ 1) and combinatorial effects that arise probabilistically. We discuss our experimental results in the context of recent pyrolysis experiments and observations of naturally occurring thermogenic methane. We consider a proposal consistent with observations from nature that the hydrogen isotope exchange reactions that promote equilibration of methane isotopic molecules at or near formation temperature may be facilitated by free radicals generated by pyrolysis reactions. In this framework, isotope exchange effectively ceases when pyrolysis effectively ceases locking in compositions that can be consistent with peak formation temperatures.

Selecting resonances in molecular scattering by anti-Zeno effect.

Utilizing the anti-Zeno effect, we demonstrate that the resonances of ultracold molecular interactions can be selectively controlled by modulating the energy levels of molecules with a dynamic magnetic field. We show numerically that the inelastic scattering cross section of the selected isotopic molecules in the mixed isotopic molecular gas can be boosted for 2-3 orders of magnitude by modulation of Zeeman splittings. The mechanism of the resonant anti-Zeno effect in the ultracold scattering is based on matching the spectral modulation function of the magnetic field with the Floquet-engineered resonance of the molecular collision. The resulting insight provides a recipe to implement resonant anti-Zeno effect in control of molecular interactions, such as the selection of reaction channels between molecules involving shape and Feshbach resonances, and external field-assisted separation of isotopes.

Stable Isotope Analysis of Greenhouse Gases Requires Analyte Preconcentration

Nitrous oxide (N2O) is an important trace gas contributing to global warming and depletion of ozone in the stratosphere. Its increasing abundance is caused mainly by anthropogenic sources, such as application of fertilizers in agriculture or emissions from industry. To understand the N2O global budget, its sources and sinks need to be well-described and quantified. In this project, a new method for N2O source appointment was developed that can help with this task. The method is based on analysis of the eight most abundant isotopic molecules of N2O, using quantum cascade laser absorption spectroscopy (QCLAS). The applicability of the method towards the N2O biogeochemical cycle was demonstrated on a prominent N2O source (bacterial denitrification) and the most important N2O sink (UV photolysis) on samples prepared in laboratory experiments. An extension of the QCLAS method to natural samples can be achieved by hyphenation with a preconcentration technique that increases concentration of the analyte and standardizes the sample matrix. This article provides an overview of currently applied preconcentration techniques in the field of greenhouse-gas analysis and a description of the preconcentration device TREX that will be employed in future projects with the developed QCLAS method.

Redox controls on H and N speciation and intermolecular isotopic fractionations in aqueous fluids at high pressure and high temperature: Insights from in-situ experiments

Aqueous magmatic fluids are essential to the transport of hydrogen (H), carbon (C), and nitrogen (N) from the mantle to the surface, during which changes in pressure, temperature, and redox conditions affect the chemical speciation and intermolecular isotopic fractionations of H, C, and N. Here, we performed a series of hydrothermal diamond-anvil cell experiments to evaluate the role of pressure, temperature, and redox conditions on the speciation and intermolecular fractionations of H and N during the decompression and cooling of aqueous fluids from 780 MPa to 800°C to 150 MPa and 200°C. We used Raman spectroscopy to investigate the distribution and exchange reactions of H and N isotopologues between water, methane, ammonia, and di-nitrogen molecules under changing physicochemical conditions. Our experiments show that upon decompression, a C- and N-bearing fluid will preferentially degas D-rich methane and 15N-rich N2, depleting the residual aqueous fluid in those isotopes. If this fluid precipitates N-rich (i.e., NH4+-bearing) minerals, the observed N isotopic fractionation is opposite to that during N2 degassing, enriching the aqueous fluid in 15N. Because these fractionations result from changes in H, C, and N speciation in the aqueous fluid, their magnitudes depend on redox conditions as well as pressure and temperature. Our new in-situ experimental results are consistent with the large H and N isotopic fractionations observed between water, methane, and ammonia species in aqueous fluids at high pressures and temperatures, although the magnitude of the fractionations in our experiments cannot be quantified. Nonetheless, our results suggest that statistical thermodynamic models likely underestimate isotopic fractionation effects for isotopic molecules under these conditions, and should account for solubility and isotopic effects of the solvent associated with the solvation of water, methane, and ammonia isotopologues in aqueous fluids.This work has significant implications for interpreting isotopic measurements of natural samples from hydrothermal systems because it offers insights into isotopic fractionations in multicomponent and multiphase systems under hydrothermal temperatures and pressures.

Isotope and Spin Effects Induced by Compression of Paramagnetic Molecules

The zero-point energies (ZPEs) of paramagnetic molecules, free and compressed in a C59N paramagnetic cage, were computed. The excess of energy acquired by molecules under compression depended on the deuterium and tritium isotopes which ranged from 6–8 kcal/mol for H2+ to 1.0–1.5 kcal/mol for HO• and HO2. The differences in the ZPEs of compressed isotopic molecules resulted in large deuterium and tritium isotope effects which differed for singlet and triplet spin states. The hyperfine coupling (HFC) constants for protons and 17O nuclei decreased under compression, confirming the leakage of the unpaired π-electron from the central oxygen atom of guest molecules into the system of π-electrons of the cage, and its distribution over 60 atoms of the C59N. The latter seems to be the reason why the nitrogen-14 HFCs for C59N remain almost unchanged upon encapsulation of guest molecules. The singlet-triplet splitting is shown to depend on the Coulomb interaction, which controls the sign of the exchange potential. The importance of compression effects on the functioning of enzymes as molecular compressing devices is discussed.

Density functional theoretical analysis of micro-adsorption of isotopes of hydrogen molecule and atom by uranium

Tritium, the heaviest among hydrogen isotopes can be safely stored as metal hydride (tritide). The (depleted) uranium metal is being considered in international thermonuclear experimental reactor (ITER) because of its compatible physicochemical properties. The fundamental understanding of U–H isotopes interaction will help in the efficient storage of H isotopes in depleted uranium metal. Hence, density functional theoretical (DFT) analysis has been performed to investigate the micro-adsorption of hydrogen and its isotopic molecules on uranium atom. The geometrical configurations of UXn, U (X2)n and UX4-(X2)n (X = H, D, T; n = 1–9) cluster were analyzed using different DFT functional (PBE, PBEO, M06 and M06-2X). In the case of U-(H2)4 and U-(H2)5, one H2 molecule was seen to be dissociated to give UH2(H2)3 and UH2(H2)4 cluster as observed earlier in the experiment. The formation of U (X2)n and UX4-(X2)n microclusters was explained by calculating binding enthalpy, natural population analysis and electron density at the bond critical points (BCP). Further, more insights were derived by computing the type of interactions between U and H2 isotopic molecules. The Kubas interaction of a U atom with a H2 molecule was identified by an elongation of the H–H bond without breakage and a reduction in its stretching frequency due to binding. The interaction of U and H2 isotopic molecules was confirmed to be Kubas type of interaction whose strength lies in between the covalent bond of metal hydrides and the van der Waals bond of materials. Further, σ-donation from H2 to d and f orbitals of U atom and π-back-donation from U to the anti-bonding orbital of H2, and atoms-in-molecules analysis indicates that the electron density at the bond critical points of the bound H2 is similar to that of Kubas systems. The Kubas type of interaction suggests that the reversible adsorption of hydrogen molecules might be favored with U metal. From structural and binding enthalpy (BE) analysis, UH4-(H2)8 polyhydride was predicted to be the largest super polyhydride and found to be stable by 8.2 kcal/mol over UH4-(H2)6 polyhydride and thus confirmed its plausibility. To the best of our knowledge UH4-(H2)8 is the largest metal polyhydride ever been reported with twenty hydrogen atoms displaying high gravimetric density of 7.80, 14.47 and 20.21 wt% for H2, D2 and T2 respectively. The present DFT results thus draw further attention for more computational and experimental studies in this important uranium-hydrogen system for efficient reuse of depleted uranium metal as tritium storage material.

Rapid detection of donor-dependent photocatalytic hydrogen evolution by NMR spectroscopy.

Understanding molecular processes at nanoparticle surfaces is essential for designing active photocatalytic materials. Here, we utilize nuclear magnetic resonance (NMR) spectroscopy to track photocatalytic hydrogen evolution using donor molecules and water isotopologues. Pt–TiO2 catalysts were prepared and used for isotopic hydrogen evolution reactions using alcohols as electron donors. 1H NMR monitoring revealed that evolution of the H2 and HD species is accompanied by the oxidation of donor molecules. The isotopic selectivity in the hydrogen evolution reaction gives rise to formal overpotential. Based on a comparison of the rates of hydrogen evolution and donor oxidation, we propose the use of ethanol as an efficient electron donor for the hydrogen evolution reaction without re-oxidation of radical intermediates.

Rotational analysis and hyperfine structures of A2Π1/2 → X2Σ1/2 transition in 25,26MgF isotope molecules

High resolution ro-vibrational spectroscopy of the A2Π1/2(v′ = 0) → X2Σ1/2(v = 0) band, for the buffer-gas-cooled magnesium monofluoride (25,26MgF) isotope molecules, has been measured by the in-cell direct absorption. Due to the decent populations in the low-lying rotational states (X2Σ1/2(v = 0, N = 0, 1)) for the cooled 25,26MgF molecules, the rotational levels and constants of the A2Π1/2(v′ = 0) state of 25,26MgF are accurately determined. Furthermore, hyperfine-structure levels of X2Σ1/2(v = 0, N = 1) of 25,26MgF are successfully measured by the laser induced fluorescence. Such studies complement previous studies on the more abundant 24MgF molecule and are useful for precision measurement and relevant laser cooling experiments.

Measurement of the permanent electric dipole moment of ultracold ground state 85Rb133Cs molecules by microwave coherent spectroscopy.

We demonstrate measurement of the permanent electric dipole moment (EDM) of 85Rb133Cs molecules in the absolute vibrational ground state by microwave (MW) coherent spectroscopy. The rotational states of the considered molecules, which are formed from short-range photoassociation of mixed cold atoms, are nondegenerated under external electric field. To measure the EDM based on electric-field-induced shifts of the sublevels of X1Σ+(v = 0, J = 1) rotational state, we utilized a MW coherent spectroscopy, which has a higher resolution than depletion spectroscopy and one-photon MW spectroscopy and can also eliminate the influence from Stark shift of the excited state existing in both spectroscopies above. In order to acquire accurate electric intensity, electromagnetic induced transparency spectroscopy of 85Rb Rydberg atoms is used to implement the calibration. The permanent EDM of 85Rb133Cs molecules is finally determined to be 1.266(15) D, which agrees with the theoretical calculations and is comparable with the value of its isotopic molecule.

Isotopic effect of macro- and microelements in ecosystems

Isotopic effects occurring in living organisms due to metabolism are analyzed. The phenomenon of metabolism is considered in the classical sense as a combination of biochemical reactions (mainly enzyma­tic) that take place in the cells of living beings and provide the cleavage, synthesis and interconversion of complex compounds. The scope of use of natural isotopes is wide and diverse. Isotopes are carriers of information about the birth and transformation of molecules, and isotope fractionation is a chemical characteristic of a substance. Isotope metabolism consists in the intermolecular fractionation of isotopes at separate stages of biochemical reactions, namely the cleavage, synthesis and interconversion of complex compounds caused by differences in the structure and fundamental properties of isotope nuclei. It is proved that the fractionation of isotopes in chemical and biochemical reactions due to isotopic effects is based on two fundamental properties of atomic nuclei — mass and magnetic moment. The kinetic (mass-depen­ dent) isotopic effect distributes the isotopic nuclei by their masses, and the magnetic one fractionates the nuclei by their magnetic moments. The kinetic isotopic effect depends on the magnitude of the difference in the masses of isotopic molecules, temperature and the difference in the activation energies of isotopic forms. The magnetic isotope effect depends on the reaction rate in a single cell, its projection, magnetic moment and energy of electron-nuclear interaction. It is determined that the fractionation of isotopes in living organisms is that the relative content of one of the isotopes in this compound increases by reducing its content in the other. As a result, there is a fractionation of isotopes within one biological object.

Generation of an intense single harmonic emission event and attosecond pulse from hydrogen molecular ion and its isotopic molecular ions with the assistance of half-cycle unipolar pulse

Through controlling the charge resonance enhanced ionization process of the isotope molecules of hydrogen molecular ion, deuterium molecular ion and tritium molecular ion, the intense single harmonic emission event has been produced, which is beneficial to generate the single attosecond pulse. Moreover, the optimal laser parameter combinations for producing the intense harmonic spectra and attosecond pulses have been shown from 4 × 1014 W/cm2 to 7 × 1014 W/cm2. Further, by properly adding a half-cycle unipolar pulse, the selected single harmonic emission event can be further extended, which can support the shorter attosecond pulse with higher photon energy. Finally, by superposing these harmonics, a number of intense attosecond pulses shorter than 40 as can be obtained.

Isotope Effects Induced by Molecular Compression.

Zero-point energies (ZPEs) of hydroxyl ion and hydrogen and water molecules, free and compressed in C60 cages, are computed; the excess energy acquired by molecules under compression is in the range 2-3 kcal/mol and depends on the isotopes. The differences in ZPE of compressed isotopic molecules strongly exceed those of the free molecules, resulting in the large deuterium and tritium isotope effects. These effects induced by compression are suggested as a probe for testing molecular compression of enzymatic sites; they may be important for understanding enormously large isotope effects observed in some enzymatic reactions, where they are attributed to the tunneling.

Pulse duration dependence of harmonic yield of H2+ and its isotopic molecule

We investigate the pulse duration dependence of harmonic yield in isotopic molecules of H2+ and T2+ driven by different laser intensities. Generally, the harmonic yield can be improved as pulse duration increases and then a maximum value can be obtained at the specific duration. Particularly, (i) driven by low laser intensity, the optimal pulse duration for H2+ is 20 cycles, and the harmonic intensity of H2+ is much higher than that of T2+. (ii) Driven by middle laser intensity, the optimal pulse durations for H2+ and T2+ are 15 cycles and 22 cycles, respectively. Moreover, the harmonic intensities of H2+ and T2+ from optimal pulse durations are almost the same. (iii) Driven by high laser intensity, the optimal pulse duration for T2+ is 15 cycles. For H2+, the enhancement of harmonic yield is very slow as pulse duration increases. Furthermore, the similar harmonic yields of H2+ and T2+ can be found before 12 cycles; while, when the pulse duration is larger than 12 cycles, the harmonic yield of H2+ is smaller than that of T2+. Taking advantage of harmonic yield changing law and with assistance of controlling pulse, the intense and broad spectral plateau can be obtained, which can support the generation of isolated attosecond pulses with durations of sub-40 as.

Annual study of hydraulic characteristics in surface flow constructed wetlands using hydrogen and oxygen stable isotope technology

Complex flow patterns and hydraulic characteristics could reduce the utilization efficiency of constructed wetland (CW), and consequently, its pollutant removal performance. Thus, it is of great importance to explore the internal flow patterns of CWs. Isotopic molecules exist naturally in CWs and have special properties under liquid conditions; using hydrogen and oxygen isotope technology cannot only reduce secondary pollution but also reflect the hydraulic characteristics of CWs. In the present study, the annual variation of isotopic composition in field-scale CW was investigated to evaluate the long-term feasibility of stable isotopic technology characterizing hydraulic flow patterns. The relationship between nutrients concentration distribution and flow pattern variation in CW under different seasons was discussed as well. Results demonstrated that isotope 18O/16O distribution could be used to determine the internal flow pattern of CW throughout the year, except for preferential flow area of CWs in winter, since more hydraulic retention time is needed to ensure the change of water isotopes due to the small evaporation in winter. Lower ammonia nitrogen concentration was observed in the stagnant area, while the total phosphorus concentration of the stagnant area increased during winter. And more attention should be paid to aquatic plants during the CW design, since it has significant influence on the hydraulic flow patterns of CW.

Decelerated Liquid Dynamics Induced by Component-Dependent Supercooling in Hydrogen and Deuterium Quantum Mixtures.

Isotopic mixtures of p-H2 and o-D2 molecules have been an attractive binary system because they include two kinds of purely isotopic molecules which possess the same electronic potential but the twice different mass inducing differently pronounced nuclear quantum effects (NQEs). Accessing details of structures and dynamics in such quantum mixtures combining complex molecular dynamics with NQEs of different strengths remains a challenging problem. Taking advantage of the nonempirical molecular dynamics method which describes p-H2 and o-D2 molecules, we found that the liquid dynamics slows down at a specific mixing ratio, which can be connected to the observed anomalous slowdown of crystallization in the quantum mixtures. We attributed the decelerated dynamics to the component-dependent supercooling of p-H2 taking place in the mixtures, demonstrating that there is an optimal mixing ratio to hinder crystallization. The obtained physical insights will help in experimentally controlling and achieving unknown quantum mixtures including superfluid.

Control of high-order harmonics from H2+ and D2+ for producing intense single attosecond pulse

Generally, the intensities of molecular high-order harmonic spectra from [Formula: see text] and its isotope molecules are quite different due to the effect of nuclear signals. Thus, in this paper, we investigate the change law of harmonic spectra from [Formula: see text] and [Formula: see text] driven by different laser fields and try to find the optimal harmonic spectra for producing intense single attosecond pulses (SAPs). The results show that in lower laser intensity case, the harmonic yield follows as [Formula: see text]; while, in higher laser intensity case, the harmonic yield meets the condition of [Formula: see text]. Further, by using this change law of harmonic yield and choosing the optimal harmonic emission peak (HEP), we can obtain the intense spectral continuum with the assistance of the half-cycle pulse (HCP). Next, with the superposition of some harmonics on the spectral continuum, the intense SAPs shorter than 37 as can be obtained from [Formula: see text] and [Formula: see text] harmonic spectra. Finally, the results show that the stronger attosecond signals can be obtained when the light nucleus or heavy nucleus molecules are driven by lower or higher laser intensities, respectively.

Probing isotope effects of oriented molecules with odd-even high-order harmonics

We study high-order harmonic generation (HHG) from oriented isotope molecules beyond the Born-Oppenheimer approximation numerically and analytically. We compare the symmetric cases of ${\mathrm{H}}_{2}$ and its isotopic variant ${\mathrm{T}}_{2}$ to the asymmetric ones of ${\mathrm{HeH}}^{+}$ and ${\mathrm{HeT}}^{+}$. Different from symmetric molecules, the laser-induced stretching for asymmetric molecules depends strongly on the molecular orientation. In addition, the structures of the HHG spectra for oriented ${\mathrm{H}}_{2}$ versus ${\mathrm{T}}_{2}$ differ remarkably from each other, and one can trace the stretching of these symmetric isotope molecules directly from the spectra. However, the spectral structures for oriented ${\mathrm{HeH}}^{+}$ versus ${\mathrm{HeT}}^{+}$ are basically the same. In this situation, we propose a procedure for probing the stretching of these asymmetric isotope molecules using odd-even HHG, with a high time-space resolution.

Isotope Selective Control over Clustering of SF6 Molecules and Dissociation of (SF6)mArn van der Waals Clusters Using an IR Laser

We present the results of an investigation into the interaction of SF6 molecules and clusters in a molecular beam with resonant IR laser radiation at different stages of the beam evolution along the axis of its propagation. The beam has been formed as a result of gas-dynamic expansion of a mixture of SF6 with argon carrier gas during expansion from a pulsed nozzle. The experimental setup and the investigation method are described. It has been shown that selective vibrational excitation of SF6 molecules with a specific sulfur isotope by a CO2 laser near the nozzle edge causes suppression of the clustering process of these isotopic molecules. Selective IR excitation of clusters under the conditions of the formed cluster beam leads to isotopically selective dissociation of clusters. Depending on the experimental conditions including different distances of the irradiation zone of particles from the nozzle edge, the results of measuring the efficiency and selectivity of molecular clustering suppression and cluster dissociation processes are presented. It has been shown that both of these processes make it possible to achieve high selectivity values for the 32S and 34S sulfur isotopes. In the case in which the clustering of SF6 molecules was selectively suppressed, selectivity values α ≥ 25–30 have been obtained. Upon selective dissociation of (SF6)2 dimers under similar expansion conditions of the gas mixture, selectivity values α ≥ 20–25 for 32SF632SF6 dimers with respect to 34SF632SF6 dimers have been obtained. Particular attention has been paid to measurements at a high dilution of SF6 in argon under conditions of predominant formation of (SF6)mArn mixed clusters. The potential of using studied processes as a basis for the technology of the laser isotope separation are discussed.