Wave Packet Research Articles

Investigation of Modulational Instability Drift Wave Packet in Non-uniform Magneto-Rotating Plasma

Investigation of Modulational Instability Drift Wave Packet in Non-uniform Magneto-Rotating Plasma

Highly enhanced reactivity of HCl on the Ag/Au(111) alloy surface via rotational quantum state excitation.

Rotational excitations of reactants are often considered to have little impact on chemical reactivity compared to the excitations of vibrational modes and translational motion. Here, we reveal a significant influence of the rotational excitation of HCl on its dissociation on an Ag/Au(111) alloy surface. This finding is based on six-dimensional time-dependent wave packet calculations performed on an accurately fitted machine learning potential energy surface. Rotational energy is found to be 90 times more effective in driving the reaction than an equivalent amount of translational energy. The reactivity of HCl on Ag/Au(111) is diminished due to a charge transfer effect, which induces a strongly non-monotonic dependence of the minimum energy path on molecular orientation, resulting in the HCl molecule deviating from the minimum barrier. We identify and detail two underlying mechanisms by which rotationally excited HCl can overcome the charge transfer effect between Au and Ag atoms, leading to enhanced reactivity and an intriguing rotational-alignment phenomenon. This finding underscores the profound impact that rotational excitations can exert on molecular reactivity, emphasizing a delicate interplay between various forms of molecular energy and their respective contributions to the reaction mechanism.

Activation of momentum fluctuations in wave packet molecular dynamics: Impacts on momentum distributions of projectile-like fragments

Activation of momentum fluctuations in wave packet molecular dynamics: Impacts on momentum distributions of projectile-like fragments

The role of the Indian Ocean Dipole in modulating the austral spring ENSO teleconnection to the Southern Hemisphere

Abstract. The combined influence of the El Niño–Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD) on the extratropical circulation in the Southern Hemisphere (SH) during austral spring is examined. Reanalyses and the large ensemble of National Centers for Environmental Prediction (NCEP) Climate Forecast System version 2 (CFSv2) model outputs were used to compute composites and linear regressions for relevant variables. The results show that a positive IOD can reinforce the El Niño-induced circulation by merging the Indian Ocean wave train with the Pacific South American (PSA) pattern over the Pacific Ocean. In addition, the results obtained with the CFSv2 model output shows that strong positive IODs can contribute to enhancing the circulation signal of the El Niño anomalies and the Indian Ocean wave train. On the other hand, negative IODs in combination with La Niña do not have that combined circulation response. While there is a moderate intensification of the circulation anomalies associated with La Niña, accompanied by some changes in the location of their main action centers, results vary considerably between linear regression, the observed composites, and model composites. Regarding the influence of the IOD activity (independent of ENSO), reanalysis-based results show that the IOD positive phase has a significant impact over the entire SH, while the negative phase is associated with weaker anomalies and less consistent atmospheric response.

Biofeedback neurotraining in the correction of emotional changes in early cerebral small vessel disease

Cerebral small vessel disease (CSVD) associated with age and vascular risk factors has a high prevalence and social significance. Psychoemotional changes are an early manifestation of CSVD that require methods for their correction. Objective: to evaluate and compare the efficacy of biofeedback (BF) at infra-low frequencies and alpha waves frequencies in correcting emotional changes in patients with early CSVD. Material and methods. The study included 71 patients (85% women; mean age 52.8±6.3 years) with early CSVD and 21 healthy volunteers (71% women; mean age 53.2±4.8 years). Patients were randomized into three groups using the envelope method with double-blind placebo control: BF-neurotraining at infra-low frequencies (n=25), alpha waves (n=22) and imitation of BF based on electroencephalography parameters (placebo; n=24). Fifteen 30-minute individual sessions were conducted 2–5 times per week. Clinical symptoms, brain MRI data and psychoemotional status were assessed in all participants before and immediately after the BF course and 6–8 weeks later. Results. Patients with early-stage CSVD were characterized by an medium level of situational and a high level of personal anxiety, mild symptoms of depression and an medium level of alexithymia. Infra-low frequencies and alpha waves BF-neurotrainings were comparable in terms of their efficacy in reducing personal anxiety. Alpha waves training also showed an effect in reducing situational anxiety in the long term. Infralow frequencies training also reduced the level of depression. Placebo training had no effect on the parameters studied. Conclusion. In patients with early CSVD, BF-neurotraining at infra-low frequencies and alpha waves may be one of the methods for correcting the emotional changes associated with CSVD.

The Strengthened Linkage between ENSO and the Eurasian Pattern since the Late 1980s

Abstract The Eurasian (EU) teleconnection pattern is an important atmospheric intrinsic mode over the extratropical Northern Hemisphere, and it has strong influence on the weather and climate over Eurasia and remote regions. Investigating factors for the EU variability is crucial and has important implications for regional climate prediction. This study reveals a remarkable influence of El Niño–Southern Oscillation (ENSO) on the EU in early winter and particularly a notable enhancement of this influence since the late 1980s. The results indicate that ENSO can lead to the vertical motion and atmospheric heating anomalies over the tropical Indian Ocean, triggering an atmospheric wave train propagating along the subtropical westerly jet and inducing an EU-like pattern over Eurasia in early winter. The interdecadal enhancement of the ENSO impact on the EU after the late 1980s may be attributable to the warming of the background mean sea surface temperature (SST) in the tropical Indian Ocean. In particular, ENSO can lead to stronger atmospheric heating and circulation anomalies over the tropical Indian Ocean via a strong air–sea interaction due to a warmer background mean SST after the late 1980s. A warmer background mean SST in the tropical Indian Ocean accelerates the subtropical westerly jet due to the thermal-wind balance, which is more favorable for the propagation of the atmospheric wave train forced by the atmospheric heating anomalies in the tropical Indian Ocean. The observed mechanisms for the enhanced impact of ENSO on the EU are also validated by numerical experiments. Significance Statement The Eurasian (EU) teleconnection pattern is an important atmospheric internal variability with significant influences on the Eurasian climate. The present study finds a remarkable relationship between the EU and ENSO in early winter, and this connection is significantly enhanced in recent decades. Thus, ENSO may serve as an important precursor signal for predicting the EU. Observational analysis and numerical experiments show that the warmer tropical Indian Ocean (TIO) plays a key role in this enhanced relationship. The warmer TIO may enhance the local air–sea interaction and accelerate the subtropical jet. The ENSO-induced anomalous disturbance over the TIO becomes stronger and can more easily propagate along the subtropical jet, exerting a strong influence on the EU especially after the late 1980s.

Vibronic Conical Intersection Trajectory Signatures in Wave Packet Coherences.

Conical intersections are ubiquitous in the energy landscape of chemical systems, drive photochemical reactivity, and are extremely challenging to observe spectroscopically. Using two-dimensional electronic spectroscopy, we observe the nonadiabatic dynamics in Wurster's Blue after excitation to the lowest two vibronic excited states. The excited populations relax ballistically through a conical intersection in 55 fs to the electronic ground state potential energy surface as the molecule undergoes an intramolecular electron transfer. While the kinetics are identical on both vibronic energy surfaces, we observe different patterns of coherent oscillations after traversing the conical intersection indicating distinct nonadiabatic relaxation pathways through the conical energetic funnel. These coherences are not created directly by the excitation pulses but are the result of the dynamical trajectories projecting differently on the conical intersection vibrational space. Our spectroscopic data offers a fresh perspective into the complex conical intersection topology and dynamics that emphasizes the critical involvement of the intersection space in dictating the dynamics.

Time-resolved Coulomb explosion imaging of vibrational wave packets in alkali dimers on helium nanodroplets.

Vibrational wave packets are created in the lowest triplet state 13Σu+ of K2 and Rb2 residing on the surface of helium nanodroplets, through non-resonant stimulated impulsive Raman scattering induced by a moderately intense near-infrared laser pulse. A delayed, intense 50-fs laser pulse doubly ionizes the alkali dimers via multiphoton absorption and thereby causes them to Coulomb explode into a pair of alkali ions Ak+. From the kinetic energy distribution P(Ekin) of the Ak+ fragment ions, measured at a large number of delays, we determine the time-dependent internuclear distribution P(R, t), which represents the modulus square of the wave packet within the accuracy of the experiment. For both K2 and Rb2, P(R, t) exhibits a periodic oscillatory structure throughout the respective 300 and 100ps observation times. The oscillatory structure is reflected in the time-dependent mean value of R, ⟨R⟩(t). The Fourier transformation of ⟨R⟩(t) shows that the wave packets are composed mainly of the vibrational ground state and the first excited vibrational state, in agreement with numerical simulations. In the case of K2, the oscillations are observed for 300ps, corresponding to more than 180 vibrational periods with an amplitude that decreases gradually from 0.035 to 0.020Å. Using time-resolved spectral analysis, we find that the decay time of the amplitude is ∼260ps. The decrease is ascribed to the weak coupling between the vibrating dimers and the droplet.

Flipping electric dipole in the vibrational wave packet dynamics of carbon monoxide

Recently, Rydberg atom-ion-bound states have been observed using a high-resolution ion microscope [Nature 605, 453 (2022)] and the corresponding vibrational dynamics has been spectroscopically analyzed. The atom-ion bond is created by an avoided crossing, which involves a flipping molecular dipole. Motivated by the discovery of the flipping dipole moment in this highly excited Rydberg system covering large spatial scales and long time scales, we address here the question of whether a flipping dipole could also occur in ground-state diatomic molecules on much smaller scales. Specifically, we investigate the vibrational wave packet dynamics within the 1 Σ g + electronic ground-state of carbon monoxide (CO). The latter shows a zero crossing of its dipole moment function close to its equilibrium. Via the time-evolution of a vibrational wave packet approximating a coherent state, we demonstrate that indeed a flipping, i.e. oscillating, dipole with a non-zero time-averaged value is obtained and its dynamics can be controlled to some extent. Varying the coherent state parameter we explore different regions of the vibrational excitation spectrum thereby tuning the time scales of the rapid oscillatory motion of the relevant observables, their decay and revivals as well as the transition to a regime of irregular dynamics.

The Influence of Arctic Oscillation on South China Precipitation in Winter Is Modulated by the Atlantic Multidecadal Oscillation

AbstractAs the dominant mode of low‐frequency atmospheric variability in extratropical Northern Hemisphere, the Arctic Oscillation (AO) exerts strong impacts on East Asian climate, with the positive AO leading to increased South China winter precipitation (SCWP). Here, we find that such AO–SCWP relationship is nonstationary and controlled by the remote Atlantic Multidecadal Oscillation (AMO). Especially, the relationship between positive AO and SCWP is significantly weakened during the warm phase of AMO. Observational analyses and idealized Atlantic pacemaker simulations indicate that warm AMO forcing is accompanied by a teleconnection wave train extending eastward from the North Atlantic to West Pacific and the western North Pacific sea surface temperature warming, which together induce northerly wind anomalies over South China by enhancing the land–ocean pressure gradient. Such climate background state changes associated with the warm AMO prohibit the positive AO induced water vapor transport to South China, thereby weakening the AO–SCWP relationship.

Correlating Double‐Cone Polariton Dynamics with Local Femtosecond Laser Modifications in Ultrashort‐Pulse‐Stimulated Crystals

AbstractStrong similarities for relativistic electrons stimulated from electron beams and electron clouds are merging the boundary of wave‐particle duality of electrons, one of which being superposition is Cherenkov radiations. Recent theoretical investigations into quantum Cherenkov effects for cone‐shape particles have hypothesized electron‐spin flip transitions in bound‐ and free‐electron systems like bulk silica and graphene. However, experimental validation of these predictions remains outstanding. Here, analogous phenomena of polariton‐version quantum Cherenkov radiations observed by broadband femtosecond pump‐probe experiments is reported, and demonstrate double‐cone emission processes involving of Cherenkov‐type phonon polaritons (PhPs) and plasmon‐PhPs in ultrashort‐pulse‐stimulated ferroelectric crystals and graphene, respectively. Through component analysis of double‐cone polariton emissions using an empirical quantum dynamics model, the initial polariton dynamics are restored by time translation corrections. The resulting quantum wave packets of PhPs are found to be correlated with femtosecond‐laser‐induced modifications inside ferroelectric lithium niobates, achieving a PhP threshold criterion for ultrasmooth femtosecond laser nanofabrication.

State-to-State Time-Dependent Quantum Dynamics Studies of the Si(3P) + OH(X 2Π) → OSi(X 1Σg+) + H(2S) Reaction Based on a New HOSi(X2A') Potential Energy Surface.

Quantum and quasi-classical dynamics calculations were conducted for the reaction of Si with OH on the latest potential energy surface (PES), which is obtained by fitting tens of thousands of ab initio energy points by using the many-body expansion formula. To obtain an accurate PES, all energy points calculated with aug-cc-pVQZ and aug-cc-pV5Z basis sets were extrapolated to the complete basis set limit. The accuracy of our new PES was verified by comparing the topographic characteristics and contour maps of potential energy with other works. In addition, the anharmonic vibrational frequencies of HOSi and HSiO based on the present ab initio and PES by means of quantum dynamics methods were calculated. Dynamics information such as reaction probability, integral cross sections (ICS), product distribution, and rate constants was obtained on the new HOSi(X2A') PES. The dynamic information calculated using the quasi-classical trajectory method and time-dependent wave packet method is generally in good agreement, except for the vibrational state-resolved ICSs of product. The calculated differential cross section and capture time reveal that the reaction is primarily governed by the complex formation mechanism.

Enhancing Gaussian quantum metrology with position-momentum correlations

Abstract Quantum metrology offers significant improvements in several quantum technologies. In this work, we propose a Gaussian quantum metrology protocol assisted by initial position-momentum correlations (PM). We employ a correlated Gaussian wave packet as a probe to examine the dynamics of Quantum Fisher Information (QFI) and purity based on PM correlations to demonstrate how to estimate the PM correlations and, more importantly, to unlock its potential applications such as a resource to enhance quantum thermometry. In the low-temperature regime, we find an improvement in the thermometry of the surrounding environment when the original system exhibits a non-null initial correlation (correlated Gaussian state). In addition, we explore the connection between the loss of purity and the gain in QFI during the process of estimating the effective environment coupling and its effective temperature.

Optical wave packet compression using counterpropagating Scorer beams

Abstract We investigate the diffractive paraxial wave equation with an external potential, utilizing self-similarity and variable separation methods. The exact solution to this evolution equation, expressed through Scorer functions, gives rise to the new Scorer beams. We explore the dynamics of counterpropagating Scorer beams, as promising optical wave packets, focusing on their compression behavior. The Scorer beams are characterized by two key parameters: the attenuation factor and the initial pulse width. By appropriately adjusting these parameters, significant beam compression can be achieved. Specifically, increasing the attenuation factor enhances compression and raises pulse amplitude, while reducing the initial pulse width further amplifies these effects. Along the way, we observe interesting interference patterns of the counterpropagating Scorer beams, never seen before. This study introduces a novel approach to beam compression and opens up new possibilities for their practical applications.

Quantum Sensitivity of a Photon-added Molecular Wave Packet

Abstract We study the temporal dynamics of a photon-added SU(2) coherent state, involving vibrational bound states of an Iodine molecule. The nonclassicality of Schrodinger cat-like and compass-like photon-added states of this anharmonic potential is explored through Mandel Q parameter and the negative region in their phase spaces. The Wigner phase space distribution is thoroughly studied for the photon added molecular state and displayed for cat- and compass-like states. Generation and control of the sub-Planck interference structures become intriguing with photon addition. We ensure that the photon addition helps to improve the quantum sensitivity for a diatomic molecular system by comparing it between photon-added and photon-subtracted states. The detailed study of quantum sensitivity reveals that, one can use a photon-added molecular wave packet as a probe to attain sensitivity to displacement, that greatly exceeds the standard quantum limit. We also report that the nature of variation of the quantum sensitivity becomes qualitatively commensurate with that of the Wigner-negativity.

Abrupt X-to-O-wave structural field transition in presence of anomalous dispersion

All linear, propagation-invariant, paraxial pulsed beams are spatiotemporally X-shaped (conical waves) in the absence of group-velocity dispersion (GVD) or in the presence of normal GVD. It is known, however, that such conical waves become O-shaped in the presence of anomalous GVD, resulting in a field profile that is circularly symmetric in space and time. To date, experiments generating conical waves in which the wavelength of a high-energy pump laser is tuned across the zero-dispersion wavelength of a nonlinear medium have not revealed the expected X-to-O-wave structural field transition. We report here an unambiguous observation of a fixed-central-wavelength X-to-O-wave structural field transition occurring in linear dispersion-free wave packets in the anomalous GVD regime, without needing to change the sign or magnitude of the GVD. Instead, by tuning the group velocity of a space–time wave packet (STWP) across a threshold value that we call the “escape velocity,” we observe an abrupt transition in the STWP from an O-shaped to an X-shaped spatiotemporal profile. This transition is associated with an abrupt change in the associated spatiotemporal spectrum of the STWP: from closed elliptical spatiotemporal spectra below the escape velocity to open hyperbolic spectra above it. These results may furnish new opportunities for engineering the phase-matching conditions in nonlinear and quantum optics.

The Joint Influences of the South Asian Jet Wave Train and Eurasian Teleconnection on the Wet–Cold Extreme over South China in February 2022

Abstract In February 2022, an extreme wet and cold event hits South China, with the regional precipitation ranking the second highest on record, while the temperature ranked the third lowest since 1979. In this study, the physical mechanisms of this extreme event are investigated from the perspective of multiple time-scale interactions. Results show that the strong confrontation between the warm and moist air advection by the India–Burma trough (IBT) and the invasion of cold air activity related to the strengthening of the East Asian winter monsoon (EAWM) is the key to trigger this extreme event. Further analyses show that the multitime-scale coupling of the South Asian jet wave train and Eurasian (EU) teleconnection is the main reason for the strong cold and warm–moist airflow. The EU teleconnection on both intraseasonal and synoptic time scales plays a key role in triggering this extreme event by strengthening the EAWM. On the synoptic time scale, not only the EU teleconnection but also the South Asian jet wave train plays a key role. They show a stronger intensity on this time scale, and their coupling is obvious. The South Asian jet wave train enhances the moisture supply by deepening the IBT, which further conflicts with the strong EAWM modulated by the EU teleconnection over South China, leading to this extreme wet–cold event. The forecast skills in the Subseasonal to Seasonal (S2S) Prediction project models of this event are evaluated in this paper, and results show that the ECMWF model can successfully predict the extreme precipitation by capturing the coupling of the two wave trains with a 5-day lead time.

Langmuir solitons in plasma with κ-deformed Kaniadakis distributed electrons in the kinetic regime

The dynamics of Langmuir solitons in plasma with κ-deformed Kaniadakis distributed electrons is studied. First, a Zakharov-type equation describing the evolution of the fields of Langmuir and ion-acoustic wave is derived in a kinetic regime. Then, in the one-dimensional case, the Zakharov-type equation is reduced to the well-known nonlinear Schrödinger equation that is applied to investigate the characteristics of modulated Langmuir wave packets. It is shown that there are two types of solitons, one is bright soliton in the subsonic regime and the other is dark soliton in the supersonic regime. It also found that when the amplitudes of both types of solitons are fixed, the width of bright soliton increases, while the width of dark soliton decreases, with increased distribution index κ. The present work may serve as a preliminary investigation into the nonlinearity of the κ-deformed Kaniadakis distributed plasma system.

Full-wavefield regularization to enhance signal-to-noise ratio in sparse low-fold land data for better reservoir attribute extraction

Sparse land seismic data, when acquired in areas with sand and detrital materials overlying faster velocity strata, are often marred by intense near-surface noise moving at slow speeds. This noise persists, even with the fine source and receiver spacing of high-channel-count 3D surveys, leading to aliasing issues. Traditional velocity-based filtering, whether in the frequency-wavenumber (f-k) or radon domains, is ineffective at removing this noise during data processing. Addressing the aliasing of slow near-surface noise through proper regularization before denoising can significantly enhance data quality. We introduce a novel approach called full-wavefield regularization and present its application for the first time on a sparse 3D low-fold offshore seismic data set. This technique aims to regularize both the seismic signals and coherent noise wave trains to a spacing where aliasing is not an issue. Consequently, the reflection and surface-wave components can be easily distinguished, and the noise can be eliminated. The results depict a marked improvement in the signal-to-noise ratio. This makes the data set usable and improves the computation of high-quality seismic attributes such as coherence and curvature, which supports better interpretation of the seismic data.

Impact of Arctic Sea ice anomalies on tropical cyclogenesis over the eastern North Pacific: Role of northern Atlantic Sea surface temperature anomalies

The present study identifies a close linkage between spring (MAM) sea ice concentration (SIC) anomalies in the Greenland-Barents (GB) Seas and the tropical cyclone (TC) genesis frequency over the eastern North Pacific (ENP) in the subsequent summer and fall (JJASON) during 1979–2022. An increase in MAM GB SIC anomalies results in a decrease in subsequent JJASON ENP TC genesis frequency. The physical process for the influence of Arctic sea ice anomalies on TC formation is further examined. Detailed dynamical diagnosis reveals that a higher GB SIC during MAM results in an increase in upward shortwave radiation, leading to sea surface temperature (SST) cooling. This SST cooling triggers a teleconnection atmospheric wave train, traversing Eurasia, the northern Pacific and the northern America and reaching the northern Atlantic. The associated anomalous cyclone over mid-latitude northern Atlantic is accompanied by anomalous southwesterly winds over the subtropics, leading to SST warming in the subtropical northern Atlantic through weakening total wind speed and upward surface latent heat flux. SST warming in the subtropical northern Atlantic extends southward into the tropical Atlantic via wind-evaporation-SST feedback during the subsequent summer and autumn, which induces an anomalous zonal-vertical circulation with descending motion over the ENP. This descending motion reduces relative humidity and weakens local convection over the ENP, and thus is unfavorable for TC genesis there. This study suggests that the spring GB SIC could serve as a potential predictor of JJASON ENP TC genesis.