Full Excitation Research Articles

Ultrafast photoinduced dynamics of single atoms solvated inside helium nanodroplets.

Helium nanodroplets can serve as reaction containers for photoinduced time-resolved studies of cold, isolated molecular systems that are otherwise inaccessible. Recently, three different dynamical processes, triggered by photoexcitation of a single atom inside a droplet, were observed in their natural time scale: Expansion of the He solvation shell (He bubble) within 600 fs initiates a collective bubble oscillation with a ∼30 ps oscillation period, followed by dopant ejection after ∼60 ps. Here, we present a systematic investigation of these processes by combining time-resolved photoelectron and photoion spectroscopy with time-dependent He density functional theory simulations. By variation of the photoexcitation energy, we find that the full excess excitation energy, represented by the blue-shifted in-droplet excitation band, is completely transferred to the He environment during the bubble expansion. Surprisingly, we find that variation of the droplet size has only a minor influence on the ejection time, providing insight into the spatial distribution of the ground-state atoms before photoexcitation. Simulated particle trajectories after photoexcitation are in agreement with experimental observations and suggest that the majority of ground-state atoms are located at around 16 Å below the droplet surface. Bubble expansion and oscillation are purely local effects, depending only on the ultimate dopant environment. These solvation-induced dynamics will be superimposed on intramolecular dynamics of molecular systems, and a mechanistic description is fundamental for the interpretation of future experiments.

Singlet (1Δg) O2 as an efficient tropospheric oxidizing agent: the gas phase reaction with the simplest Criegee intermediate.

The reaction between CH2OO and 1Δg O2 has been investigated by means of high level quantum chemical and chemical kinetic calculations. Post-CCSD(T) corrections in terms of full triplets and partial quadratic excitations, along with core corrections have been employed to estimate the reaction energetics. The title reaction was found to be effectively barrierless with the transition state lying -22.85 kcal mol-1 below the isolated reactants. Rate coefficients under tropospheric conditions have been calculated using the master equation. The calculated rate coefficient was found to be marginally over the gas kinetic limit, implying that the reaction rate would be limited by the upper limit of bimolecular collision frequency. When compared against ˙OH and O3, 1O2 was found to compete efficiently with the two well known tropospheric oxidants.

Measurement of Nuclear Lifetimes and B(E2) Values in 130Xe as a Test for E(5) Symmetry

As a continuation of the previous measurement in 128Xe [1], [2], [3], another E(5) candidate, 130Xe, has been studied through the novel experimental technique Coulex-plunger in inverse kinematics. The measurements have been undertaken at the JYFL accelerator facility in Jyvaskyl ̈a, Finland. For the purpose of this experiment the Cologne plunger was coupled to the JYFL cyclotron which delivered the 130Xe beam. Excited states in 130Xe were populated by the natFe(130Xe, 130Xe*) reaction at E(130Xe)=500 MeV and the subsequent de-excitations were detected in the JUROGAM γ-ray array. By applying the well known Differential Decay Curve Method (DDCM) [4], lifetimes of the 2^+_1 and 4^+_1 excited states were determined. In addition, since the investigated nucleus is excited through the Coulomb interaction, it is possible to perform a full Coulomb excitation analysis of the data using the computer code GOSIA [5] which will allow the determination of B(E2) values of the transitions up to the 6^+_1 excited state.

Unraveling the excitation spectrum of many-body systems from quantum quenches

Quenches are now routinely used in synthetic quantum systems to study a variety of fundamental effects, including ergodicity breaking, light-cone-like spreading of information, and dynamical phase transitions. It was shown recently that the dynamics of equal-time correlators may be related to ground-state phase transitions and some properties of the system excitations. Here, we show that the full low-lying excitation spectrum of a generic many-body quantum system can be extracted from the after-quench dynamics of equal-time correlators. We demonstrate it for a variety of one-dimensional lattice models amenable to exact numerical calculations, including Bose and spin models, with short- or long-range interactions. The approach also applies to higher dimensions, correlated fermions, and continuous models. We argue that it provides an alternative approach to standard pump-probe spectroscopic methods and discuss its advantages.

High-Level Ab Initio Predictions for the Ionization Energy, Bond Dissociation Energies, and Heats of Formation of Vanadium Methylidyne Radical and Its Cation (VCH/VCH+).

The ionization energy (IE) of VCH, the 0 K V-CH/VC-H bond dissociation energies (D0s), and the heats of formation at 0 K (ΔHf0°) and 298 K (ΔHf298°) for VCH/VCH+ are predicted by the wave function-based CCSDTQ/CBS approach. This composite-coupled cluster method includes full quadruple excitations in conjunction with the approximation to the complete basis set (CBS) limit. The contributions of zero-point vibrational energy, core-valence (CV) correlation, spin-orbit coupling, and scalar relativistic corrections are taken into account. The present calculations show that adiabatic IE(VCH) = 6.785 eV and demonstrate excellent agreement with an IE value of 6.774 7 ± 0.000 1 eV measured with two-color laser-pulsed field ionization-photoelectron spectroscopy. The CCSDT and MRCI+Q methods which include CV correlations give the best predictions of harmonic frequencies: ω2 (ω2+) (bending) = 534 (650) and 564 (641) cm-1 and the V-CH stretching ω3 (ω3+) = 835 (827) and 856 (857) cm-1 compared with the experimental values. In this work, we offer a streamlined CCSDTQ/CBS approach which shows an error limit (≤20 meV) matching with previous benchmarking efforts for reliable IE and D0 predictions for VCH/VCH+. The CCSDTQ/CBS D0(V+-CH) - D0(V-CH) = -0.012 eV and D0(VC+-H) - D0(VC-H) = 0.345 eV are in good accord with the experimentally derived values of -0.028 4 ± 0.000 1 and 0.355 9 ± 0.000 1 eV, respectively. The present study has demonstrated that the CCSDTQ/CBS protocol can be readily extended to investigate triatomic molecules containing 3d-metals.

Sequential excitations of Peregrine solution structures in combined Ma breathers for a (3+1)-dimensional coupled partially nonlocal nonlinear Schrödinger equation

We find a combined Ma-breather solution of a (3+1)-dimensional coupled partially nonlocal nonlinear Schrödinger equation with variable coefficients, where nonlinearities are localized in x and y directions and non-localized in the z-direction. Sequential excitations of Peregrine solution structures in combined Ma breathers including the full excitation, prohibitive excitation, crest excitation and persistent excitation are discussed by contrasting values between the maximum of accumulated time and every crest location of Peregrine solution structures in combined Ma breathers.

A Tear-Drop Bifilar Sample Holder for Full Excitation and Stability Studies of HTS Cables at 4.2 K Using a Superconducting Transformer

HTS cables proposed for next-generation main, hybrid, and insert magnets will have very high I c (>10 kA) at 14 T and above. Determining the quench, current-sharing, and other properties of these cables will require measurement systems, which will likely incorporate a superconducting transformer. The utilization of high-field persistent mode solenoids will make size and cost less prohibitive, allowing a higher frequency of measurements within a larger number of research facilities. Additionally, a system designed for use with solenoids will allow for experiments at higher maximum fields than those achievable using dipoles and split coils. Proposed in this document is a bifilar sample probe, which fits within a 77-mm bore solenoid capable of measuring up to a 6-mm outer diameter conductor-on-round-core REBCO cables or wires up to 20 kA in transverse fields at 12 T and 4.2 K. Splices and mechanical considerations will be discussed.

Many-body effects on Equation of state of solid Ar4

Based on the first-principles, using many-body expansion method and the double cluster with full single and double excitations plus perturbative treatment of triples (CCSD(T)) calculation method and augmented correlation consistent quadruple zeta (aug-cc-pVQZ) basis set, many-body contributions to the equation of state (EOS) of solid argon are accurately calculated with the atomic distance R from 2.0Å to 3.6Å at the room temperature (T=300K) in the experimentally studied range of pressures (0∼80GPa). In addition, we obtain the two- and three-body potential energies of fcc solid Ar. The results showed that, only taking into account the two-body potential, our calculated results were in good agreement with the experimental values, the results of GGA and LDA at the low-pressure regions (<15GPa). Further adding three-body term up to 80GPa, and it may be helpful to accurately explain the phenomenon of the experiment above 80GPa when the effect of four-body and higher-body potential pressures are considered.

Performance enhancement of 64 Gb/s OFDM system at 1550 nm over multimode fiber using Volterra equalization

Based on a developed analytical model, we demonstrate the feasibility of intensity-modulation direct-detection (IM/DD) optical orthogonal frequency division multiplexing (OOFDM) system over 1 km of multimode fiber (MMF) at data rates up to 64 Gb/s, at 1550 nm. The effect of data rates, number of subcarriers and fiber length are investigated for different number of excited mode groups that can be generated using the offset launch technique. Indeed, we show that when we increase the efficiency of the Volterra equalizer, by raising its input taps from 7 to 9, we can reduce the system impairments of 5.45 dB in terms of Q factor at 800 m. Furthermore, we prove that by exciting more mode groups the MMF bandwidth is reduced potentially. Finally, thanks to the efficiency of Volterra equalizer, we achieve a bit error rate (BER) below the forward error correction (FEC) limit, even in the case of the full excitation technique.

Calculation of reactions cross section for proton-induced nuclear reactions on Iodine-127 isotope

Radioisotope production for nuclear medicine is tomography devices. Both single photon emissions computed tomography (SPECT) and positron emission tomography (PET) is used for diagnosis in nuclear medicine we have calculated the reaction cross section and investigated the excitation functions for the formation of 127,126 125 I , 126,127,128 Xe , 126,125 Te isotopes in the interactions of proton particle with the nucleus of the iodine-127 isotope. The analysis shows that there is a variation of interaction cross-section with a variation of energy of the incident particle. The result shows that the plots of the 127 I (p,ng), and 127 I (p,2ng), graphs have full excitation curve. The productions confirm the presence of Xenon-127 and Xenon-126 isotopes are possible at the energy range of 0 to 30 MeV from the iodine-127 nucleus. Keywords : Cross-Section; Excitation function; Nuclear Reaction; Radioisotope; Statistical Multistep Reaction

Near-white photoluminescence in paramagnetic Gd6O5F8 nanoparticles

White light emission has been achieved by near full band excitation from 10.7 nm sized pure Gd6O5F8 nanoparticles.

Noncovalent Interactions between Molecular Hydrogen and the Alkali Fluorides: H-H···F-M (M = Li, Na, K, Rb, Cs). High Level Theoretical Predictions and SAPT Analysis.

Various types of hydrogen bonds have been recognized during the past century. In this research, a new type of noncovalent interaction, the dipole-induced hydrogen bond formed between a hydrogen molecule and an alkali halide, H-H···F-M, is studied. Proposed by Zhang and co-workers ( Phys. Chem. Chem. Phys. 2015, 17, 20361), these systems are extensively investigated initially using the "gold standard" CCSD(T) method in conjunction with augmented correlation-consistent polarized core-valence basis sets up to quadruple-ζ. The full triple excitations CCSDT method has been used to further refine the energies. Several properties including geometries, bond energies, vibrarional frequencies, charge distributions, and dipole moments have been reported. The earlier Zhang research considered only the linear H-H···F-M structures. However, we find these linear stationary points to be separated by very small barriers from the much lower lying bent C s structures. The CCSDT/aug-cc-pCVQZ(-PP) method predicts the dissociation energies for bent H-H···F-M (M = Li, Na, K, Rb, Cs) are 2.76, 2.96, 3.00, 2.89, and 2.49 kcal mol-1, respectively, suggesting that the H···F hydrogen bond becomes gradually stronger when alkali metal M goes down the periodic table from Li to K but becomes slightly weaker for Rb and even more for Cs. This Li < Na < K > Rb > Cs order is consistent with that for the dipole moments for the isolated MF (M = Li, Na, K, Rb, Cs) diatomics. Symmetry adapted perturbation theory (SAPT) is used to understand these unusual noncovalent interactions.

Dual-Wavelength Temporal Dynamics of a Gain-Switched 2-μm Tm3+:Lu2O3 Ceramic Laser

We provide a detailed experimental investigation of the energy efficiency and rich temporal dynamics of a gain-switched 2-μm Tm3+:Lu2O3 ceramic laser pumped near 800 nm. A tunable Ti3+:sapphire laser was used to determine the full excitation spectrum and the optimum pumping bands for the 1.5% Tm3+:Lu2O3 ceramic gain medium. These bands were centered at 774, 796, and 811 nm. The highest output pulse energy was obtained when the pump wavelength was set to 796 nm. In the experiments, a free-running x-cavity was used to investigate the energy efficiency of the Tm 3+:Lu2O3 ceramic laser. Extracavity grating-dispersed output and prism-tuned resonator were used to further assess the role of cross-relaxation for the 1.5% Tm3+:Lu2 O3 ceramic. Finally, we demonstrate that as the pump energy was increased, a transition occurred from single-wavelength output (2068 nm) to dual-wavelength multipulse output (2068 and 1968 nm). We performed systematic temporal and spectral characterization measurements by using the free-running resonator, extracavity-grating-dispersed laser output, and prism-tuned resonator to investigate how the laser pulses at 1968 and 2068 nm evolved in time. A plane-wave rate equation model was further used to investigate the temporal dynamics of the Tm3+:Lu2O3 ceramic laser and provided predictions in qualitative agreement with experimental data.

Impact of Post-CCSD(T) Corrections on Reaction Energetics and Rate Constants of the OH• + HCl Reaction.

High level ab initio calculations have been performed to predict the reaction energy and barrier height for the OH• + HCl reaction. After including the effect of full quadratic excitations at the coupled cluster level, in addition to core, relativistic, spin-orbit, and diagonal Born-Oppenheimer corrections, we found the values of reaction energy and barrier height to be -15.29 and +2.38 kcal mol-1, respectively. Employing this reaction energy and barrier height, we used variational transition state theory in conjunction with small curvature tunneling to calculate the rate constants within a temperature range from 138 to 1000 K. The calculated rate constants were found to be in good agreement with available experimental results throughout the whole temperature range.

Measurement of the full excitation spectrum of the 7Li(p,γ)αα reaction at 441 keV

A current challenge for ab initio calculations is systems that contain large continuum contributions such as Be8. We report on new measurements of radiative decay widths in this nucleus that test recent Green's function Monte Carlo calculations.Traditionally, γ ray detectors have been utilized to measure the high energy photons from the Li7(p,γ)αα reaction. However, due to the complicated response function of these detectors it has not yet been possible to extract the full γ ray spectrum from this reaction. Here we present an alternative measurement using large area Silicon detectors to detect the two α particles, which provides a practically background free spectrum and retains good energy resolution.The resulting spectrum is analyzed using a many-level multi channel R-matrix parametrization. Improved values for the radiative widths are extracted from the R-matrix fit. We find evidence for significant non-resonant continuum contributions and tentative evidence for a broad 0+ resonance at 12MeV.

Noise analysis and improvement of a micro-electro-mechanical-systems fluxgate sensor

An integrated micro solenoid fluxgate sensor with a Co-based amorphous core is presented in this work based on the Micro-Electro-Mechanical System (MEMS) technologies. As the advantage of miniaturization, the micro fluxgate sensor is found to be operated under wide excitation frequency range of 100 kHz–1 MHz. Ultra-low frequency noise (<0.1 Hz) always arises in zero field time-domain signal acquisition under full excitation frequency range. An additional broadband transformer is placed before the excitation end of the sensor to eliminate the ultra-low frequency noise. The noise power density of the sensor working at 600 kHz is analyzed. The result shows the noise is 1.15 nT/Hz1/2@1 Hz without the transformer and 0.11 nT/Hz1/2@1 Hz with the transformer, while the noise rms level is 5.38 nT and 0.23 nT in the frequency range of 50 mHz–10 Hz respectively. For the MEMS micro fluxgate sensor, more stringent electromagnetic compatibility design for the sensor signal system is needed to eliminate additional noise derived from the electromagnetic radiated interference and the voltage disturbance.

Non-iterative triple excitations in equation-of-motion coupled-cluster theory for electron attachment with applications to bound and temporary anions.

The impact of residual electron correlation beyond the equation-of-motion coupled-cluster singles and doubles (EOM-CCSD) approximation on positions and widths of electronic resonances is investigated. To establish a method that accomplishes this task in an economical manner, several approaches proposed for the approximate treatment of triple excitations are reviewed with respect to their performance in the electron attachment (EA) variant of EOM-CC theory. The recently introduced EOM-CCSD(T)(a)* method [D. A. Matthews and J. F. Stanton, J. Chem. Phys. 145, 124102 (2016)], which includes non-iterative corrections to the reference and the target states, reliably reproduces vertical attachment energies from EOM-EA-CC calculations with single, double, and full triple excitations in contrast to schemes in which non-iterative corrections are applied only to the target states. Applications of EOM-EA-CCSD(T)(a)* augmented by a complex absorbing potential (CAP) to several temporary anions illustrate that shape resonances are well described by EOM-EA-CCSD, but that residual electron correlation often makes a non-negligible impact on their positions and widths. The positions of Feshbach resonances, on the other hand, are significantly improved when going from CAP-EOM-EA-CCSD to CAP-EOM-EA-CCSD(T)(a)*, but the correct energetic order of the relevant electronic states is still not achieved.

Singlet exciton condensation and bond-order-wave phase in the extended Hubbard model

The competition of interactions implies the compensation of standard mechanisms which leads to the emergence of exotic phases between conventional phases. The extended Hubbard model (EHM) is a fundamental example for the competition of the local Hubbard interaction and the nearest-neighbor density-density interaction, which at half-filling and in one dimension leads to a bond order wave (BOW) between a charge density wave (CDW) and a quasi-long-range order Mott insulator (MI). We study the full momentum-resolved excitation spectrum of the one dimensional EHM in the CDW phase and clarify the relation between different elementary energy gaps. We show that the CDW-to-BOW transition is driven by the softening of a singlet exciton at momentum $\pi$. The BOW is realized as the condensate of this singlet exciton.

S54 Motor axon excitability changes during anti-epileptic voltage-gated NA+ channel blocker therapy

Objectives Anti-epileptic drugs targeting voltage-gated Na channels (VGSC) are not selective for the brain. The aim of this study was to investigate the excitability of myelinated median nerve motor axons in epileptic patients treated with carbamazepine and other anti-VGSC drugs. Methods Stimulation was carried out at wrist and evoked compound muscle action potential (CMAP) was recorded from the abductor pollicis brevis muscle. Multiple measures of motor excitability using the TRONDNF protocol were carried out using an automatic threshold-tracking setup. In addition, the current required to evoke threshold responses targeting 40–50% of maximal CMAP amplitude was also determined by manual trial-and-error, for cathodic pulses of 0.2, 0.5 and 1 ms duration to measure the strength-duration time constant (SDTC). Results Across the anti-VGSC treated group there was an impairment in motor axon excitability with a 30% reduction in SDTC as compared to age-matched normal controls. A similar reduction in SDTC could be detected by manual threshold tracking in 3 different laboratories, using conventional nerve conduction equipment. The time for manual SDTC measurements was comparable to the full automatic multiple excitability measures protocol. Discussion The excitability impairment by partial VGSC block did not affect conduction of normal motor axons. Conclusions Our data suggest that, at the therapeutic doses of anti-VGSC drugs, there is an impairment in motor axon excitability that can be measured with conventional neurophysiological equipment. Significance Nerve excitability measurements could prove useful for monitoring the functional consequences of the anti-VGSC therapy in epilepsy.

CO2 infrared emission as a diagnostic of planet-forming regions of disks

[Abridged] The infrared ro-vibrational emission lines from organic molecules in the inner regions of protoplanetary disks are unique probes of the physical and chemical structure of planet forming regions and the processes that shape them. The non-LTE excitation effects of carbon dioxide (CO2) are studied in a full disk model to evaluate: (i) what the emitting regions of the different CO2 ro-vibrational bands are; (ii) how the CO2 abundance can be best traced using CO2 ro-vibrational lines using future JWST data and; (iii) what the excitation and abundances tell us about the inner disk physics and chemistry. CO2 is a major ice component and its abundance can potentially test models with migrating icy pebbles across the iceline. A full non-LTE CO2 excitation model has been built. The characteristics of the model are tested using non-LTE slab models. Subsequently the CO2 line formation has been modelled using a two-dimensional disk model representative of T-Tauri disks. The CO2 gas that emits in the 15 $\mu$m and 4.5 $\mu$m regions of the spectrum is not in LTE and arises in the upper layers of disks, pumped by infrared radiation. The v$_2$ 15 $\mu$m feature is dominated by optically thick emission for most of the models that fit the observations and increases linearly with source luminosity. Its narrowness compared with that of other molecules stems from a combination of the low rotational excitation temperature (~250 K) and the inherently narrower feature for CO2. The inferred CO2 abundances derived for observed disks are more than two orders of magnitude lower than those in interstellar ices (~10$^5$), similar to earlier LTE disk estimates. Line-to-continuum ratios are low, of order a few %, thus high signal-to-noise (S/N > 300) observations are needed for individual line detections. Prospects of accurate abundance retreival with JWST-MIRI and JWST-NIRSpec are discussed.