Solid Krypton Research Articles

Safety and therapeutic efficacy of 577 nm yellow solid krypton laser for retinopathy of prematurity; A prospective pilot study.

To evaluate the outcome of 577 nm yellow solid krypton laser as an independent treatment modality for Retinopathy of Prematurity. Prospective, non-comparative, non-randomized, interventional. A prospective pilot study was conducted on 30 treatment eyes with retinopathy of prematurity (ROP) who underwent treatment with a 577 nm yellow solid state krypton laser. 3nethraNEO pediatric retinal imaging system was used to screen these infants born between March to August 2022. Pre procedure data such as gestational age (weeks), birth weight (g), and exposure to risk factors were recorded. Power (mW), exposure duration (msec), and number of laser spots administered were noted. Pain was assessed using the Neonatal Pain/Agitation and Sedation Scale (N-PASS). Post procedure data such as regression, persistence or reactivation of disease, and adverse effects were looked for. All eyes were followed up for a period of 3 months. Chi-square test, Fisher's exact test. Out of 30 eyes, 09 (30%) had type I and 21 (70%) had non-type I ROP. In type I disease, the mean power used was 88+/-10 mW with exposure duration of 130+/-27 msec and an average number of 890+/-260 burns were administered. In non-type I disease, the mean power used was 87+/-10 mW with an exposure duration of 150 ms and an average number of 900+/-290 burns were administered. The mean pain score calculated was 5 in type I and 6 in non-type I ROP. All eyes showed regression of disease after treatment. 577 nm yellow solid krypton laser was safe and effective in treating retinopathy of prematurity disease.

Dynamics of Electronically Excited Metal Atoms (Zn and Cd) in Rare Gas Matrices: Simulation of Multiple-band Emission using Molecular Dynamics with Quantum Transitions.

Molecular dynamics with quantum transitions approach is employed to simulate the spectroscopic characteristics of the 1 P1 ↔1 S0 transitions in atomic zinc and cadmium in order to gain insight into the excited state behavior of these atoms isolated in solid rare gases neon, argon, and krypton. The absorption and emission spectra are simulated. Non-radiative processes play a fundamental role in the transfer of population among the three electronic states initially accessed in absorption. Three distinct relaxation pathways were identified. Two of these are related to the dynamical modes described in previous works [McCaffrey and Kerins, J. Chem. Phys. 106, 7885 (1997); Kerins and McCaffrey, J. Chem. Phys. 109, 3131 (1998)] in which the system evolves to form a square planar configuration around the metal atom. The third distinct pathway involves motion on a hexagonal close packed plane. The temperature dependence of complex formation was also determined for the three relaxation pathways.

Martensitic fcc-hcp transformation pathway in solid krypton and xenon and its effect on their equations of state

The martensitic transformation is a fundamental physical phenomenon at the origin of important industrial applications. However, the underlying microscopic mechanism, which is of critical importance to explain the outstanding mechanical properties of martensitic materials, is still not fully understood. This is because for most martensitic materials the transformation is a fast process that makes in situ studies extremely challenging. Noble solids krypton and xenon undergo a progressive pressure induced fcc to hcp martensitic transition with a very wide coexistence domain. Here, we took advantage of this unique feature to study the detailed mechanism of the transformation by employing in situ X-ray diffraction and absorption. We evidenced a four stages mechanism where the lattice mismatch between the fcc and hcp forms plays a key role in the generation of strain. We also determined precisely the effect of the transformation on the compression behavior of these materials.

(Noble Gas)n -NC+ Molecular Ions in Noble Gas Matrices: Matrix Infrared Spectra and Electronic Structure Calculations.

An investigation of pulsed‐laser‐ablated Zn, Cd and Hg metal atom reactions with HCN under excess argon during co‐deposition with laser‐ablated Hg atoms from a dental amalgam target also provided Hg emissions capable of photoionization of the CN photo‐dissociation product. A new band at 1933.4 cm−1 in the region of the CN and CN+ gas‐phase fundamental absorptions that appeared upon annealing the matrix to 20 K after sample deposition, and disappeared upon UV photolysis is assigned to (Ar) n CN+, our key finding. It is not possible to determine the n coefficient exactly, but structure calculations suggest that one, two, three or four argon atoms can solvate the CN+ cation in an argon matrix with C−N absorptions calculated (B3LYP) to be between 2317.2 and 2319.8 cm−1. Similar bands were observed in solid krypton at 1920.5, in solid xenon at 1935.4 and in solid neon at 1947.8 cm−1. H13CN reagent gave an 1892.3 absorption with shift instead, and a 12/13 isotopic frequency ratio–nearly the same as found for 13CN+ itself in the gas phase and in the argon matrix. The CN+ molecular ion serves as a useful infrared probe to examine Ng clusters. The following ion reactions are believed to occur here: the first step upon sample deposition is assisted by a focused pulsed YAG laser, and the second step occurs on sample annealing: (Ar)2 ++CN→Ar+CN+→(Ar) n CN+.

Radiation-induced closure of the second aromatic ring: Possible way to PAH starting from a styrene-acetylene complex

The radiation-induced assembling of the naphthalene molecule was first directly observed under X-ray irradiation of the isolated styrene-acetylene complex in a solid krypton matrix at 6 K using FTIR spectroscopy. The observation of naphthalene radical cation in the presence of electron scavenger suggests a cationic pathway of this reaction. This finding makes it possible to propose a new mechanism for the formation of polycyclic aromatic hydrocarbons in astrochemical ices.

Phosphorescence excitation mapping and vibrational spectroscopy of HC9N and HC11N cyanopolyynes in organic solvents

Cyanopolyyne molecules, HC9N and HC11N, were isolated in solutions and UV, IR, and resonance Raman spectra were measured for the study of their electronic and vibrational properties. Strong signals were observed both in the IR and resonance Raman spectra for the stretching vibrational mode of the sp-hybridized linear carbon chain in the electronic ground state, i.e., σ4 at 2141 cm−1 for HC9N and σ6 at 2105 cm−1 for HC11N. Trapped in cryogenic solid acetonitrile matrix hosts at 20 K, transitions in phosphorescence, a˜3Σ+ → X˜1Σ+, were observed for HC9N at 582.3 nm (0–0) and longer wavelengths and for HC11N at 643.7 nm (0–0) and longer wavelengths. Electronic transitions in the UV, 1Σ+ ← X˜1Σ+, were elucidated by phosphorescence excitation mapping to observe asymmetric patterns with sharp emission-absorption features explainable by Shpolsky effects. For HC9N, three distinct trapping sites were discernible in solid acetonitrile, while the phosphorescence spectra were blurred in solid n-hexane. The observed phosphorescence lifetime of HC9N was longer than that of HC11N, comparable to the trend reported for the series of cyanopolyyne molecules in solid krypton matrix hosts.

Theoretical characterization of the photochemical reaction CO2 + O(3P) → CO + O2 related to experiments in solid krypton

Formation and decomposition of the complex of carbon dioxide and atomic oxygen are characterized by quantum chemistry methods aiming to rationalize experimental studies in solid krypton. The observed FTIR spectra reflected the temporal evolution of the system after irradiation showing the bands of reactants, intermediates and products. Advanced quantum chemistry calculations show that the T-shape complex CO2…O(3P) can be formed in the matrix. Its excitation by the 193 nm light results in the charge-transfer state CO2+…O−, which evolves to the reaction intermediate CO3. The latter species decomposes to CO + O2 following pathways on the excited state energy surfaces.

Carbene-insertion noble gas compounds: FKrCF and FXeCF

FKrCF and FXeCF were synthetized in solid krypton and xenon matrices at cryogenic temperatures. These molecules representing a new class of noble-gas compounds are formed as a result of reaction between mobile F atoms and trapped CF fragment in solid Kr and Xe, which occur after X-ray radiolysis of CH2F2 in the corresponding matrices. The assignment was based on comparison with previously published computational data (Chopra et al., Chem. Phys., 2017, 494, 20) and the results of additional quantum chemical calculations. New molecules were found to be sensitive to near-IR, visible and UV light.

Structural transformations in N2–Kr alloys

The structural characteristics of N2–Kr alloys were studied using electron diffraction over the entire range of mutual concentrations. The samples were prepared in situ by condensing a gaseous mixture on aluminum and carbon substrates at temperatures of 5 and 20 K. The structure and solubility regions of the solutions were determined. The maximum solubility values of the components were: less than 20 mol.% for krypton in a nitrogen crystal, and less than 11 mol.%. for nitrogen in solid krypton. Phase separation of the solid solution was observed in a concentration range of 20–89 mol.% Kr. The effect of diluting the molecular matrix with krypton on the orientational ordering of N2 molecules in the solutions was investigated. An experimental dependence of the orientation order parameter on the solution composition was determined for N2-based solutions.The structural characteristics of N2–Kr alloys were studied using electron diffraction over the entire range of mutual concentrations. The samples were prepared in situ by condensing a gaseous mixture on aluminum and carbon substrates at temperatures of 5 and 20 K. The structure and solubility regions of the solutions were determined. The maximum solubility values of the components were: less than 20 mol.% for krypton in a nitrogen crystal, and less than 11 mol.%. for nitrogen in solid krypton. Phase separation of the solid solution was observed in a concentration range of 20–89 mol.% Kr. The effect of diluting the molecular matrix with krypton on the orientational ordering of N2 molecules in the solutions was investigated. An experimental dependence of the orientation order parameter on the solution composition was determined for N2-based solutions.

Quantum dynamics and spectroscopy of dihalogens in solid matrices. I. Efficient simulation of the photodynamics of the embedded I2Kr18 cluster using the G-MCTDH method.

The molecular dynamics following the electronic BΠu30+⟵XΣg+1 photoexcitation of the iodine molecule embedded in solid krypton are studied quantum mechanically using the Gaussian variant of the multiconfigurational time-dependent Hartree method (G-MCTDH). The accuracy of the Gaussian wave packet approximation is validated against numerically exact MCTDH simulations for a fully anharmonic seven-dimensional model of the I2Kr18 cluster in a crystal Kr cage. The linear absorption spectrum, time-evolving vibrational probability densities, and I2 energy expectation value are accurately reproduced by the numerically efficient G-MCTDH approach. The reduced density matrix of the chromophore is analyzed in the coordinate, Wigner and energy representations, so as to obtain a multifaceted dynamical view of the guest-host interactions. Vibrational coherences extending over the bond distance range 2.7 Å < RI-I < 4.0 Å are found to survive for several vibrational periods, despite extensive dissipation. The present results prepare the ground for the simulation of time-resolved coherent Raman spectroscopy of the I2-krypton system addressed in Paper II.

Pressure effects on EXAFS Debye-Waller factor and melting curve of solid krypton

The pressure effects on atomic mean-square displacement, extended X-ray absorption fine structure (EXAFS) Debye-Waller factor and melting temperature of solid krypton have been investigated in within the statistical moment method scheme in quantum statistical mechanics. By assuming the interaction between atoms can be described by Buckingham potential, we performed the numerical calculations for krypton up to pressure 120 GPa. Our calculations show that the atomic mean-square displacement and EXAFS Debye-Waller factor of krypton crystal depend strongly on pressure. They make the robust reduction of the EXAFS peak height. Our results are in good and reasonable agreements with available experimental data. This approach gives us a relatively simple method for qualitatively calculating high-pressure thermo-physical properties of materials. Moreover, it can be used to verify future high-pressure experimental and theoretical works.

Effect of the fcc-hcp martensitic transition on the equation of state of solid krypton up to 140 GPa

Solid krypton (Kr) undergoes a pressure-induced martensitic phase transition from a face-centered cubic (fcc) to a hexagonal close-packed (hcp) structure. These two phases coexist in a very wide pressure domain inducing important modifications of the bulk properties of the resulting mixed phase system. Here, we report a detailed in situ x-ray diffraction and absorption study of the influence of the fcc-hcp phase transition on the compression behavior of solid krypton in an extended pressure domain up to 140 GPa. The onset of the hcp-fcc transformation was observed in this study at around 2.7 GPa and the coexistence of these two phases up to 140 GPa, the maximum investigated pressure. The appearance of the hcp phase is also evidenced by the pressure-induced broadening and splitting of the first peak in the XANES spectra. We demonstrate that the transition is driven by a continuous nucleation and intergrowth of nanometric hcp stacking faults that evolve in the fcc phase. These hcp stacking faults are unaffected by high-temperature annealing, suggesting that plastic deformation is not at their origin. The apparent small Gibbs free-energy differences between the two structures that decrease upon compression may explain the nucleation of hcp stacking faults and the large coexistence domain of fcc and hcp krypton. We observe a clear anomaly in the equation of state of the fcc solid at \ensuremath{\sim}20 GPa when the proportion of the hcp form reaches $\ensuremath{\sim}20%$. We demonstrate that this anomaly is related to the difference in stiffness between the fcc and hcp phases and propose two distinct equation of states for the low and high-pressure regimes.

Hydrogen-bridge Si(μ-H)3CeH and inserted H3SiCeH molecules: Matrix infrared spectra and DFT calculations for reaction products of silane with Ce atoms

Reactions of laser-ablated cerium atoms with silane were investigated by matrix isolation infrared spectroscopy and theoretical calculations. The reaction products, Si(μ-H)3CeH, H3SiCeH, H2Si(μ-H)CeH and HSi(μ-H)2CeH were identified on the basis of the SiD4 isotopic substitutions and DFT frequency calculations. In the solid argon or krypton matrix, the inserted H3SiCeH molecule was observed as initial product on deposition, which rearranged to hydrogen bridge species Si(μ-H)3CeH on follow-up annealing through H2Si(μ-H)CeH and HSi(μ-H)2CeH species. The SiHCe hydrogen bridge was investigated by NBO and ELF analysis. Calculation suggested that in Si(μ-H)3CeH molecule Ce atom donated one electron to Si atom, resulting in electron-rich SiH3 subunit, which was confirmed by ESP and AIM analysis. The increased basicity of SiH bond facilitates the formation of hydrogen bridge bond between Si and Ce. For comparison only insertion H3CCeH structure was obtained from the reaction of Ce atoms with CH4.

Construction of a surface positronium lifetime spectroscopy apparatus with a spin-polarized low energy positron beam

We have developed a surface positronium (Ps) lifetime spectrometer. A spin-polarized slow positron beam is generated by a sodium-22 source and a solid krypton moderator and transported to the sample chamber by electrostatic lenses. The incident energy is adjusted by a retarding potential using a deceleration tube. For the lifetime measurement, the start signal is obtained from a secondary-electron detector installed in front of the sample. The stop signal is detected by a scintillation detector for annihilation gamma rays. As a performance test, Ps lifetime measurements were carried out and clear decay curves derived from ortho-Ps self-annihilation were successfully observed. This system might be used for the estimation of the spin polarization at the surface of ferromagnetic materials.

Multilevel perspective on high-order harmonic generation in solids

We investigate high-order harmonic generation in a solid, modeled as a multi-level system dressed by a strong infrared laser field. We show that the cutoff energies and the relative strengths of the multiple plateaus that emerge in the harmonic spectrum can be understood both qualitatively and quantitatively by considering a combination of adiabatic and diabatic processes driven by the strong field. Such a model was recently used to interpret the multiple plateaus exhibited in harmonic spectra generated by solid argon and krypton [Ndabashimiye {\it et al.}, Nature 534, 520 (2016)]. We also show that when the multi-level system originates from the Bloch state at the $\Gamma$ point of the band structure, the laser-dressed states are equivalent to the Houston states [Krieger {\it el al.} Phys. Rev. B 33, 5494 (1986)] and will therefore map out the band structure away from the $\Gamma$ point as the laser field increases. This leads to a semi-classical three-step picture in momentum space that describes the high-order harmonic generation process in a solid.

Structure and properties of the radiation-induced intermediates produced from HCN in noble gas matrices

In this work we report the results of systematic studies on the radiation-induced transformations in HCN/Ng systems (Ng=Ne, Ar, Kr or Xe) at 7K using a combination of FTIR and EPR spectroscopy. It was shown that HCN underwent efficient decomposition producing H atoms, CN radicals and HNC isomer. The thermally induced reactions of H atoms in different matrices result in the formation of two isomeric radicals, H2CN and trans-HCNH, the former being predominated. The temperature dependent dynamics of CN and H2CN radicals in a krypton matrix was observed by EPR spectroscopy in solid krypton. The vibrational frequencies, IR intensities and magnetic resonance parameters of H2CN and trans-HCNH radicals calculated at the CCSD(T) level are in reasonable agreement with the experimental results. It was found that HCNH radical could be effectively bleached with visible light. The comparison of experimental and computational data made it possible to assign a new vibrational band at 918cm−1 in an Ar matrix (and the corresponding bands in Kr and Xe) to trans-HCNH radical. In addition, HKrCN was found in the case of krypton, whereas HXeCN and HXeNC were produced in solid xenon. The reaction mechanisms and contribution of different channels are discussed.

Many-body interaction and equation of state for solid krypton from ab initio calculation

Using the many-body expansion method and the double cluster with full single and double excitations plus perturbative treatment of triples [CCSD(T)] and augmented correlation consistent quadruple zeta (aug-cc-pVQZ) basis set, many-body contributions to the cohesive energy and equation of state of face-centered cubic solid krypton were accurately calculated with the atomic distance R from 2·1 to 4·0 Å at the room temperature (T = 300 K) in the experimentally studied range of pressures (0–60 GPa). The results showed that many-body expansion potential of face-centered cubic solid krypton was an exchange convergent series, and the even many-body contributions to the cohesive energy were repulsive, whereas the odd many-body contributions to the cohesive energy were attractive. For the same atomic distance R, many-body potential energy would reduce when the many-body number increases. When the atomic distance R>3·4 Å, the interaction energy may be well-described by two-body potential energy. In the range of 2·4–3·4 Å, it needs to consider three-body potential energy. Below 2·4 Å, the four-body potential energy should be considered. Finally, it was studied that the isothermal compression properties of solid krypton at the pressure regions P < 60 GPa. The research results showed that the calculated and experimental results have a good consistency at the pressure ranges 0–60 GPa, and may be helpful to accurately explain the phenomenon of the experiment above 60 Gpa when the effects of four-body, five-body potential pressure are considered.

Kinetics and mechanism of the radiation-chemical synthesis of krypton hydrides in solid krypton matrices

The processes occurring in the X-irradiated C2H2/Kr and HCl/Kr systems in the temperature range of 7–30 K were studied using a combination of FTIR and EPR spectroscopy. In both cases, irradiation results in effective decomposition of isolated molecules (C2H2 or HCl) and production of trapped H atoms. The thermal decay of trapped atoms in solid krypton was attributed to “local” reactions (below 21 K) and long-range mobility activated in the temperature range of 23–27 K. Two krypton hydrides, HKrCCH and HKrCl, were synthesized from the radiation-induced hydrogen atoms. In the case of C2H2/Kr system, competitive reaction channels of H atoms at various absorbed doses were investigated in details, and HKrCCH was found to be one of the main reaction products. The X-ray radiolysis in krypton matrices was concluded to be a promising method to obtain krypton hydrides.

Investigation of alkali metal polyfluorides by matrix-isolation spectroscopy

From CsF crystals to molecular polyfluorides.

Formation and spectroscopy of dicyanotriacetylene (NC₈N) in solid Kr.

Thermally induced creation of dicyanotriacetylene (NC8N) was observed in solid krypton. Samples were obtained by cryogenic trapping of gaseous cyanoacetylene/Kr mixtures subjected to electric discharges. Strong a (3)Σ(+)(u) → X (1)Σ(+)(g) phosphorescence of NC8N is reported here for the first time; its vibronic structure permitted the measurement of several ground-state vibrational frequencies. Other chemical species, mostly smaller than the precursor molecule, have also been formed, among them the dicarbon molecule (C2), and these may serve as indispensable building blocks in the NC8N synthesis. Processes leading to the elongation of cyanoacetylenic chains are of potential importance for the chemistry of icy grains present in the interstellar gas clouds.