Atomic and Molecular Physics

Miniature atomic beams can provide new functionalities for atom based sensing instruments such as atomic clocks and interferometers. We recently demonstrated a planar silicon device for generating well-collimated thermal atomic beams [Nat Commun 10, 1831 (2019)]. Here, we present a near-source fluorescence spectroscopy (NSFS) technique that can fully characterize such miniature beams even when measured only a few millimeters from the nozzle exit. We also present a recipe for predicting the fluorescence spectrum, and therefore, the source angular distribution, even under conditions of strong laser saturation of the probing transition. Monte Carlo simulations together with multi-level master equation calculations fully account for the influence of optical pumping and spatial extension of the Gaussian laser beam. A notable consequence of this work is the agreement between theory and experimental data that has allowed fine details of the angular distribution of the collimator to be reso...

Non-equilibrium plasma in high-voltage gas discharges of the so-called apokamp type (blue jets, red sprites) is of great interest for science and practice [1]. But, despite the advances in apokamp plasma physics, the mechanism of apokamp plasma chemistry is not very clear, in particular, concerning electronically excited reactive oxygen and nitrogen species (RONS). We tried to study this issue in more detail. Experiments were done in various oxygen-nitrogen mixtures employing electrical and optical diagnostics. Measurements showed that apokampic plasma processes are accompanied by the formation of long-lived RONS. Computational modeling by using 0D-kinetic and 1D-fluid models, including ionization, excitation, dissociation-recombination, vibrational relaxation, collisional quenching, and radiation, revealed the most probable mechanisms of plasma-chemical reactions in apokamp plasma jets. Effects of metastable RONS involving singlet oxygen O∗2(a,b), O∗(1D) and nitrogen N∗2(A), N∗(2D) were examined. The study confirms the role of long-lived RONS in apokamp plasma and indicated the way to a more efficient apokamp process. [1] E.A. Sosnin et al., JETP Lett. 103 (12):761 (2016).

We review one of the most versatile theoretical approaches to the study of time-dependent correlated quantum transport in nano-systems: the non-equilibrium Green's function (NEGF) formalism. Within this formalism, one can treat, on the same footing, inter-particle interactions, external drives and/or perturbations, and coupling to baths with a (piece-wise) continuum set of degrees of freedom. After a historical overview on the theory of transport in quantum systems, we present a modern introduction of the NEGF approach to quantum transport. We discuss the inclusion of inter-particle interactions using diagrammatic techniques, and the use of the so-called embedding and inbedding techniques which take the bath couplings into account non-perturbatively. In various limits, such as the non-interacting limit and the steady-state limit, we then show how the NEGF formalism elegantly reduces to well-known formulae in quantum transport as special cases. We then discuss non-equilibrium tra...

In this letter, we study the indirect detection of Cosmological Constant from an open quantum system of N entangled spins, weakly interacting with a thermal bath, a massless scalar field minimally coupled with the static De Sitter background, by computing the spectroscopic shifts. By assuming pairwise entanglement between spins, we construct entangled N states using a generalisation of the superposition principle. We have found that in the realistic large N limit, where the system consists of N∼ O(10^3-10^4) spins, the corresponding spectroscopic shifts, caused by the effective Hamiltonian of the system due to Casimir Polder interaction with the bath, play a crucial role to determine the observationally consistent Cosmological Constant, Λ∼ O(10^-122) (Planckian units) in the static patch of De Sitter space.

In this study, optical Bloch equations with and without neighboring hyperfine states near the degenerate two-level system (DTLS) in the challenging case of $$^{85}$$ 85 Rb D2 transition, which involves the Doppler broadening effect, are solved. The calculated spectra agree well with the experimental results obtained based on the coupling-probe scheme with orthogonal linear polarizations of the coupling and probe fields. The mechanisms of electromagnetically induced absorption (electromagnetically induced transparency) for the open $$F_g=3 \\rightarrow F_e=2$$ F g = 3 → F e = 2 and 3 transitions (open $$F_g=2 \\rightarrow F_e=2$$ F g = 2 → F e = 2 and 3 transitions) are determined to be the effect of the strong closed $$F_g=3 \\rightarrow F_e=4$$ F g = 3 → F e = 4 transition line (strong closed $$F_g=2 \\rightarrow F_e=1$$ F g = 2 → F e = 1 transition line); this finding is based on a comparison between the calculated absorption profiles of the DTLS without neighboring states and those o...

We studied the effect of the phenothiazine (PTZ) surface doping on the structural and optical properties of nanocrystalline titanium dioxide powder with a single anatase phase (A-TiO2). We found that the mixing and interaction of PTZ and A-TiO2 leads to the intense dark-blue color of PTZ-doped A-TiO2 (A/PTZ). The appearance of new bands in the Fourier transform IR spectrum indicated the formation of PTZ •+ radical cations and reduced Ti3+ species as well as extra oxygen vacancies (VO) in the TiO2 matrix. The UV-vis absorption spectrum of A/PTZ exhibited an increase in absorption in the visible region (> 400 nm). The doping of A-TiO2 with PTZ causes a noticeable redshift of the absorption edge and a significant narrowing of the band gap by 0.24 and 0.49 eV for direct and indirect electronic transitions, respectively. The photoluminescence spectra show that the photo-luminescence originating from Ti3+ and [VO-Ti3+] states for A/PTZ is stronger than for A-TiO2 , but the excitonic ph...

The demand for nanoscale materials of ultra-high purity and narrow size distribution is addressed. Clusters of Au, C60, H2 O, and serine
are produced inside helium nanodroplets using a combination of ionization, mass filtering, collisions with atomic or molecular vapor, and
electrostatic extraction, in a specific and novel sequence. The helium droplets are produced in an expansion of cold helium gas through a
nozzle into vacuum. The droplets are ionized by electron bombardment and subjected to a mass filter. The ionic and mass-selected helium
droplets are then guided through a vacuum chamber filled with atomic or molecular vapor where they collide and “pick up” the vapor. The
dopants then agglomerate inside the helium droplets around charge centers to singly charged clusters. Evaporation of the helium droplets is
induced by collisions in a helium-filled radio frequency (RF)-hexapole, which liberates the cluster ions from the host droplets. The clusters are
analyzed with a time-of-flight mass spectrometer. It is demonstrated that using this sequence, the size distribution of the dopant cluster ions
is distinctly narrower compared to ionization after pickup. Likewise, the ion cluster beam is more intense. The mass spectra show, as well,
that ion clusters of the dopants can be produced with only few helium atoms attached, which will be important for messenger spectroscopy.
All these findings are important for the scientific research of clusters and nanoscale materials in general.

We use the temporal Fourier transform of time-resolved x-ray scattering, known as Fourier-transform inelastic x-ray scattering (FT-IXS), to examine the harmonic, anharmonic, and dissociative dynamics of molecular iodine. This method can directly extract dissociation velocities. OCIS codes: (320.7150) Ultrafast spectroscopy, (320.2250) Femtosecond phenomenon, (340.7440) X-ray imaging Fourier-transform inelastic x-ray scattering (FT-IXS) has enabled Mariano et al to obtain dispersion curves for germanium to arbitrary precision [1]. We have extended FT-IXS to gas-phase systems to enable easy identification of harmonic, anharmonic, and dissociative motion. The anharmonic vibrations and dissociations of molecular iodine have been studied in our previous work [2,3], which focused on doing a spatial reconstruction of the time-resolved x-ray scattering (TRXS) signal. Here we take the FT-IXS approach whereby the temporal-Fourier transform of the TRXS signal is used to obtain a dispersion plot for the system. This dispersion plot is similar to traditional spectroscopies as we now discuss with two important distinguishing factors: (1) the dispersion plot can be obtained to arbitrary frequency resolution and (2) we can identify dissociations and their velocities. The advantage of FT-IXS to the standard spatial reconstruction of time-resolved x-ray scattering is ease of computation. Spatial reconstructions are limited because time-resolved x-ray scattering has a limited Q range at present, making reconstruction of the pair-correlation function difficult and ill-defined. Temporal Fourier transforms by comparison are easy because of the ability in an experiment to scan a nearly unlimited range of pump-probe delays. The spectrum obtained by the temporal Fourier transform has a resolution given by and a maximum observable frequency given by , where is the time resolution of the experiment and is the range of the measured pump-probe delays. To compute the temporal-Fourier transforms shown in Figure 2, the fast Fourier transform of is used, where is the radially-integrated polarization-correction scattering signal from [3]. The ease of computation comes at the cost of ease of interpretation. Here we discuss the interpretation of FT-IXS from gas-phase molecules, and we highlight its most notable feature: measuring dissociation velocities. Figure 1 shows the schematic for the TRXS experiment we conducted at LCLS in 2016 [2] as well as an example difference scattering signal at the detector for an x-ray to optical delay of 120 fs. The relevant electronic states accessible by the 520 and 800 nm pump wavelengths used in the experiment are depicted in Figure 2. Figure 3 shows the FT-IXS spectra for the two wavelengths. At 800 nm, the iodine is photoexcited through a vibrational Raman process, inducing a vibrational wavepacket on the ground X state. The excited vibrational states lie in the harmonic parts of the well, so we only observe the harmonic beat frequency in the FT-IXS spectrum as expected. At 520 nm, the iodine is photoexcited the anharmonic region of the B state. In this case, we observe both the fundamental and the second harmonic of the beat frequency, consistent with the anharmonic well. Also at 520 nm, iodine is photoexcited to the dissociative B" state, which is observable in the FT-IXS spectrum as a sloped line. The slope of this line is the velocity of the dissociating iodine molecules as given by. This highlights a novel feature of FT-IXS that cannot be obtain with traditional spectroscopies: we can directly observe and fingerprint dissociation in the spectrum. Moreover, the FT-IXS spectrum extends traditional spectroscopies as FT-IXS contains not only temporal-frequency information but also spatial-frequency information that can be used to interpret dissociative and vibrational motion in the spectrum. In summary, we provide a first extension of FT-IXS to gas-phase TRXS experiments. We believe this provides a new and exciting way of analyzing TRXS experiments such as [Co(terpy)2] 2+ which exhibits clear vibrations at [4] and cyclohexadiene which has a ring opening, similar to a dissociation process, at [5]. CLEO 2018

In order to insure the end results of the special theory of relativity, the fundamental quantities, period of time T0, the size of the space r0, and the clock mass M0, i.e. the compound mass carrying the clock labor, depicted by any given object, must already at rest, be interrelated with each other, in just a given manner, more specifically, that delineated by the cast T0 ∼ M0r0^2. This provides us with a simple relationship for any wave-like object, which can be checked right away in cases where the proportionality constant coming into play, can be considered, the same throughout. This simple finding led us to a whole new systematization for diatomic molecules, and in general, for all types of molecules.

20th International Conference on Biochemistry, Biophysics and Molecular Biology.

Doxorubicin (DOX) is a chemotherapeutic agent used for treatment of different cancers and its clinical usage is hindered by the oxidative injury-related cardiotoxicity. This work aims to declare if the harmful effects of DOX on heart can be alleviated with the use of Coenzyme Q10 (CoQ10) or L-carnitine. The study was performed on seventy two female Wistar albino rats divided into six groups, 12 animals each: Control group; DOX group (10mg/kg); CoQ10 group (200mg/kg); L-carnitine group (100mg/kg); DOX+CoQ10 group; DOX+L-carnitine group. CoQ10 and L-carnitine treatment orally started 5days before a single dose of 10mg/kg DOX that injected intraperitoneally (IP) then the treatment continued for 10days. At the end of the study, serum biochemical parameters of cardiac damage, oxidative stress indices, and histopathological changes were investigated. CoQ10 or L-carnitine showed a noticeable effects in improving cardiac functions evidenced reducing serum enzymes as serum interleukin-1 beta (IL-1 β), tumor necrosis factor alpha (TNF-α), leptin, lactate dehydrogenase (LDH), Cardiotrophin-1, Troponin-I and Troponin-T. Also, alleviate oxidative stress, decrease of cardiac Malondialdehyde (MDA), Nitric oxide (NO) and restoring cardiac reduced glutathione levels to normal levels. Both corrected the cardiac alterations histologically and ultrastructurally. With a visible improvements in α-SMA, vimentin and eNOS immunohistochemical markers. CoQ10 or L-carnitine supplementation improves the functional and structural integrity of the myocardium.

KEYWORDS:
Cardiotoxicity; CoQ10 and L-carnitine; Dox; Vimentin; eNOS

An experimental investigation was made of radiative recombination of chlorine atoms in order to study the feasibility of developing a gasdynamic recombination laser utilizing electronic phototransitions. Nonequilibrium atomic concentrations were obtained using a method of thermal dissociation of molecular chlorine in a shock tube followed by rapid cooling in a supersonic nozzle. Small-scale nozzles were used for rapid cooling. Recombination luminescence at high (>10^17 cm*3) nonequilibrium atomic concentrations was observed for the first time experimentally. The downstream distribution of the radiation intensity in the supersonic nozzles was studied. It was found that the radiation was in the near infrared in the 800-1100 nm range. A shift of the spectra toward the red and narrowing with cooling was observed. A theoretical estimate was made of the rate of vibrational relaxation of chlorine molecules under the experimental conditions. It was shown that light amplification should occur for phototransitions to high vibrational levels of the ground state. From measurements of the absolute radiation intensity in various spectral ranges, it was possible to estimate the gains feasible under experimental conditions: (5 X10^-4)—10^-2 cm*-1.

The process of two-and three-particle photorecombination of chlorine atoms in a reflected shock wave and in a supersonic nozzle has been studied. The rate constants of photorecombination between 960 K and 2800 K have been determined experimentally for the first time. The contribution of A and B states of chlorine molecules to the total radiation has been estimated and identification of the spectral distribution of the recombinative emission intensity has been carried out.

We report on ab initio coupled-cluster calculations of the interaction potential energy surface for the HCNH + –He complex. The aug-cc-pVTZ Gaussian basis, to which is added a set of bond functions placed at mid-distance between HCNH + center of mass and He atom is used. The HCNH + bonds length are set to their values at the equilibrium geometry, i.e., r e [HC] = 1.0780 Å, r e [CN] = 1.1339 Å and r e [NH] = 1.0126 Å. The interaction energy presents a global minimum located 266.9 cm −1 below the HCNH + –He dissociation limit. Using the interaction potential obtained, we have computed rotational excitation cross sections in the close-coupling approach and downward rate coefficients at low temperature (T ≤ 120 K). It is expected that the data worked out in this study may be beneficial for further astrophysical investigations as well as laboratory experiments .

Accurate molecular data for the low-lying states of SiO are computed and used to calculate rate constants for radiative association (RA) of Si and O. Einstein A-coefficients are also calculated for transitions between all of the bound and quasi-bound levels for each molecular state. The radiative widths are used together with elastic tunnelling widths to define effective RA rate constants which include both direct and indirect (inverse pre-dissociation) formation processes. The indirect process is evaluated for two kinetic models which represent limiting cases for astrophysical environments. The first case scenario assumes an equilibrium distribution of quasi-bound states and would be applicable whenever collisional and/or radiative excitation mechanisms are able to maintain the population. The second case scenario assumes that no excitation mechanisms are available which corresponds to the limit of zero radiation temperature and zero atomic density. Rate constants for SiO formation in realistic astrophysical environments would presumably lie between these two limiting cases.

It is customary in ab initio electronic structure theory to employ the clamped nucleus model; treating electrons as quantum particles and nuclei as point charges. While this model works well in most cases, in the non-adiabatic processes, e.g., electron coupled proton transfer, or when light particles like muons or positrons are added to a molecule it is no longer legitimate to employ the model and the proton, muon or positron must be also considered as a quantum particle. This means that the whole arsenal of ab initio methodologies developed within context of the clamped nucleus model is of no use and novel methodologies must be developed for such situations. In the last two decades, many such methodologies have been developed that the Nuclear-Electronic Orbital methodology (usually called NEO) is a prime example. Like the usual ab initio methodologies, the NEO has a hierarchical structure and as a first step the NEO-Hartree-Fock equations are introduced while in next steps various types of correlations, i.e., electron-electron and electron-nucleus (or muon, or positron) are introduced. More recently it has been shown that the NEO-Hartree-Fock equations are hugely simplified if one uses a Hartree type wavefunction for the quantum nuclei and this simplification maybe extended also to the NEO-density functional theory. Very recently we have demonstrated that this simplified NEO-Hartree-Fock equations can be transformed into a new set of “effective” Hartree-Fock equations in which the nucleus/muon/positron disappears as a quantum particle while the external potential experienced by electrons becomes non-Coulombic. It has been shown that the same trick also works for the NEO-density functional theory equations and an effective density functional theory emerges from the transformation. In this talk, various aspects of this novel effective theory are discussed and potential applications are considered in some detail.

Time-resolved femtosecond x-ray diffraction patterns from laser-excited molecular iodine are used to create a movie of intramolecular motion with a temporal and spatial resolution of 30 fs and 0.3 Å. This high fidelity is due to interference between the nonstationary excitation and the stationary initial charge distribution. The initial state is used as the local oscillator for heterodyne amplification of the excited charge distribution to retrieve real-space movies of atomic motion on ångstrom and femtosecond scales. This x-ray interference has not been employed to image internal motion in molecules before. Coherent vibrational motion and dispersion, dissociation, and rotational dephasing are all clearly visible in the data, thereby demonstrating the stunning sensitivity of heterodyne methods.

The Summary Einsteinian formula , declaring equivalence of such incompatible concepts as matter and its energy (i.e. finally its velocity) contradicts logic and common sense. Mass deficit revealed during measuring atomic masses of chemical elements has not to be qualified as an equivalent of binding energy, presumably used by nature to bind nucleons in atomic nucleus. Nucleons of atomic nuclei are bound together by the ethereal pressure. Mass deficits revealed during measuring atomic masses of chemical elements result from systematical errors of measurement ensuing from impossibility of the precise positioning of nuclides during their deflection by magnetic flow in mass-spectrometer. Solar energy creation by thermonuclear reaction of obtaining helium atoms from atoms of hydrogen is an unconfirmed and rather misleading hypothesis. Conducting in terrestrial conditions a thermonuclear reaction similar to the hypothetical solar one remains unsuccessful, not because of impossibility to imitate on Earth the solar conditions, but rather because of the principal impossibility of its conducting in any conditions.-One of the most extravagant and widely promoted conclusions of the Special relativity theory of Albert Einstein has become his statement on the equivalence of mass and energy, incarnated in formula Absurdity of the statement declaring the equivalence of incomparable items had not obstructed its acceptance by the scientific community, which could rather be explained by their shortage of just that common sense that according to the same Einstein is a collection of prejudices acquired before 18 years. It seemed, and such an idea was obtruded upon common people, that the sacramental formula had to open way to produce necessary kinds of matter, as well as to utilize unnecessary matter to obtain unlimited amounts of energy. Further precisions though had substantially restricted the range of efficiency of the above formula declaring that the energy could not be obtained from all matter, but only from such its part that enters atomic nucleus in form of certain binding energy.

В работе представлен анализ температурных зависимостей коэффициента поглощения звука, a·f-2 (f,T), сверхкритических флюидов: н-амиловый спирт-нитрометан и нитробензол-гексан для различных частот (5-2800) МГц, выше критической температуры расслоения вдоль изоконцентрат. Для растворов с критиче-ской концентрацией обнаружены два вида аномалий температурных зависимостей a·f-2 (f,T): универсальные (ωτ<<1) и неуниверсальные (ωτ>>1), связанные с различными флуктуационными процессами: стабильны-ми и метастабильными. Показано, что универсальная стабильная флуктуационная область (5≤f≤110) МГц, обусловлена взаимодействием звуковой волны с флуктуациями концентрации. Неуниверсальность про-являют наблюдаемые аномалии температурных зависимостей a·f-2 (f,T) в метастабильной флуктуационной области (110≤f≤2800) МГц. Как стабильная, так и метастабильная флуктуационные области также связаны с молекулярными механизмами. Для растворов с некритической концентрацией и индивидуальных ком-понентов подобных аномалий не обнаружено. Анализ аномального поведения коэффициента поглощения звука в широком частотном диапазоне неоценим для практического использования сверхкритических флю-идов в новейших технологиях. Ключевые слова: коэффициент поглощения звука, флуктуации концентрации, метастабильная флук-туационная область, критические параметры, сверхкритические флюиды, изоконцентрата. The paper presents an analysis of the temperature dependence of the sound absorption a·f-2 (f,T) of the supercritical fluids: n-amyl alcohol-nitromethane and nitrobenzene-hexane to the upper critical temperature of stratification in a wide concentration and frequency (5-2800) MHz range. The observed temperature dependence of the anomaly is associated with various fluctuation processes: stable (5≤f≤110) MHz and metastable (110≤f≤2800) MHz. It is shown that the universal stable fluctuation region is due to the interaction of sound waves with fluctuations of concentration. The observed temperature dependence of fluctuations in the metastable region has non-universal character. The stable and metastable fluctuation regions are also associated with molecular mechanisms. Analysis of the anomalous behavior of the coefficient of sound absorption in a wide frequency range is valuable for practical use of supercritical fluids in up-to-date technologies.

Results from the first radial measurements of the n = 2 to n = 1 x-ray transitions of high-Z elements in deuterium tokamak plasmas are presented. The observed line intensity ratios cannot be explained by electron-impact excitation and dielectronic recombination processes. Radiative and charge-transfer recombination are proposed as additional population mechanisms. The emission lines emitted in the cascade following capture constitute a unique diagnostic probe of the neutral component of plasmas.

Synchrotron radiation-based experimental techniques are largely employed for the characterization of the reactivity of finite size systems; in particular, x-ray absorption spectroscopy (XAS) is a suitable tool to shed light on the local electronic structure and chemical status of atoms in nano-objects, as it is very sensitive to the local bonding environment of the probed site. In supported clusters intrinsic properties and reactivity are largely distorted and obscured by the changes imposed by the growth procedure and by the influence of the substrate, so the attainability of experiments on free clusters reacting with species in the gas phase is a primary goal in the development of cluster science.
In this paper we report a proof of principle of the applicability of gas phase XAS technique to titanium and titanium oxide, hydride and hydrate systems. Experiments are performed by coupling a pulsed microplasma cluster source (PMCS) with a third generation synchrotron light source, and measuring the intensity of the electron yield coming from the interaction of VUV photons with the clusters seeded in a supersonic beam.

POST #1, POST #2 & POST #3 were recently uploaded to this site; Post #1 gave a general introduction and view of the electron. Post #2 gave a mathematical derivation of such electron. Post #3 explained how the electron charge worked. In this short post, comments are made to clarify what the electron’s electric field is. Related comments on EM waves are also included.

A computed list of transition lines for the atomic ion C+ is generated using R-matrix, Autostructure and Emissivity codes. These lines are produced by dielectronic recombination and subsequent cascade decays of the low-lying autoionizing states above the threshold of C2+1Se with a principal quantum number n<5 for the captured electron. The line list contains 6187 optically-allowed transitions which include many C II lines observed in the astronomical spectra. Beside the transition lines, the data also include level energies for the bound and resonance states, radiative transition probabilities, recombination rate coefficients, and oscillator strengths. A 26-term C2+ atomic target was used within an intermediate coupling scheme in the production of these data. The theoretical results for energy and fine structure splitting agree very well with the available experimental data for both resonances and bound states. The data were also validated by comparison to theoretical data previously reported in the literature which include radiative transition probabilities, effective dielectronic recombination rate coefficients and autoionization probabilities.

Resonances, which are also described as autoionizing or quasi-bound states, play an important role in the scattering of atoms and ions with electrons. The current article is an overview of the main methods, including a recently-proposed one, that are used to find and analyze resonances.

The current paper presents atomic data generated to investigate the recombination lines of C II in the spectra of planetary nebulae. These data include energies of bound and autoionizing states, oscillator strengths and radiative transition probabilities, autoionization probabilities, and recombination coefficients. The R-matrix method of electron scattering theory was used to describe the C2+ plus electron system.

We experimentally demonstrate how magnetic depolarization of velocity-selective optical pumping can be used to single out the collisional cusp kernel best describing spin and velocity relaxing collisions between potassium atoms and low pressure helium. The range of pressures and transverse fields used simulate the novel optical pumping regime pertinent to sodium guidestars employed in adaptive optics. We measure the precession of spin-velocity modes under the application of transverse magnetic fields, simulating the natural configuration of mesospheric sodium optical pumping in the geomagnetic field. We also provide a full theoretical account of the experimental data using the recently developed cusp kernels, which realistically quantify velocity damping collisions in this novel optical pumping regime. A single cusp kernel with a sharpness $s=13\pm 2$ provides a global fit to the K-He data.