CyberSec Research

Non-equilibrium molecular dynamics (NEMD) simulations were used to study pool boiling of water films on an ultra-thin planar aluminum substrate as well as the effect of surface wettability. The simulation geometry is a 10 nm-thick water film on an FCC aluminum substrate heated from 300 K to 900 K. The first peak acceleration onset time of the film, as the measure of the nucleation start, has been observed. The average heating rates of the near-wall water were 0.064, 0.048, and 0.035 K/ps for hydrophilic, neutral, and hydrophobic surfaces, respectively. Boiling curves shows that the critical heat flux (CHF) equals 5216, 3979, and 2525 MW/m^2 at wall temperatures of 466, 502, and 561 K, respectively. The minimum heat flux (MHF, Leidenfrost point) is equal to 2157, 2463, and 2366 MW/m^2 at wall temperatures of 767, 784, and 746 K, respectively. Interfacial HTC remains higher for longer times under the hydrophilic condition, whereas Kapitza resistance is low initially but then increases sharply after transition to film boiling with the highest values for the hydrophobic surface. In general, the results demonstrate that engineering aluminum wettability towards intense hydrophilicity diminishes the explosive boiling point, increases CHF, and enhances nanoscale thermal management performance.

The microhydration of rock salt (NaCl) molecules was investigated using high-resolution Penning ionization electron spectroscopy (PIES) in helium nanodroplets. Although model calculations predict that NaCl molecules are fully submerged inside the droplets, PIES of NaCl are highly resolved, in stark contrast to other molecular species. Co-doping the droplets with a controlled number of $n=5$--10 water molecules leads to efficient quenching of the NaCl Penning ionization signal and to its full suppression for $n\gtrsim 30$. Accompanying density-functional theory (DFT) and force field calculations reveal a transition from contact ion pair structures to solvent-separated ion pairs at $n=12$--15. However, it takes $n\approx 17$ water molecules to form a complete solvation shell around the Cl$^-$ anion and as many as $n\approx 34$ to fully hydrate the Na$^+$ cation, thus the entire NaCl molecule, which rationalizes the experimental findings.

Building on our prior work, where our team transcended self assembled molecular monolayers (SAMs) research from a 2D configuration to 3D structured materials and successfully introduced the molecular self assembled 3D printer to fabricate technomolecular materials hybrid carbon metal nanosheets that mimic biological self assembly through cooperative organic inorganic interactions these materials promise advances in nanotechnology by enabling seamless integration of molecular systems with metallic electrodes. Here we show that electron beam irradiation induces direct self patterning of silver fractal nanoelectrodes on the technomolecular nanosheets, with formation influenced by molecular structure: saturated variants yield localized nanoparticles, while conjugated ones produce propagated fractals via electron delocalization and cross linking. In situ transmission electron microscopy reveals dynamic diffusion aggregation mechanisms, allowing controlled circuit patterns through resist free electron beam lithography. This approach advances flexible electronics, bioelectronics, and energy conversion, including fractal antennas and unclonable identifiers.

Nitrogen-vacancy (NV) centers in diamond are widely used in the development of a number of sensors. The sensitivity of these devices is limited by both the number of centers used and their coherent properties. While the effects on the coherent properties of paramagnetic impurities such as carbon 13-isotopes and p1 centers are rather well understood, the mutual interaction of NV centers, which becomes especially important in relatively dense NV ensembles, is less well understood. Here, we provide a systematic study of NV-NV interaction using a dynamical double electron-electron resonance sequence, making it possible to directly observe the interaction of NV centers. Two types of dynamical DEER sequences were considered, consisting of 3 and 4 pulses. The nature of the phase jump in the 3-pulse sequence was attributed to the effect of non-commuting rotations within the sequence. Both the phase of the state vector rotation and its amplitude decay were studied, thus presenting a complete picture of decoherence due to NV-NV interaction. It was shown that the rate of the state vector decay differed significantly from predictions for a spin 1/2 system. However, the decay rate observed in the DEER sequence remained a reliable indicator of the concentration of bath spins and could be used to measure NV center concentration, provided that the magnetic transition of NV centers is saturated.

Velocity-map imaging of electrons is a pivotal technique in chemical physics. A recent study reported a quantum offset as large as 0.2 cm-1 in velocity imaging-based electron spectrometry [Phys. Rev. Lett. 134, 043001 (2025)]. In this work, we assess the existence this offset through a combination of simulations and experiments. Our simulations reveal that the velocity imaging results reconstructed using the maximum entropy velocity Legendre reconstruction (MEVELER) method exhibit no such offset. Furthermore, experimental measurements of the electron affinity of oxygen conducted at various imaging voltages show no discernible offset attributable to the electric field in the photodetachment region. Therefore, we conclude that there is no evidence for the claimed quantum offset in properly analyzed velocity imaging-based electron spectrometry.

We present an investigation of one-photon valence-shell photoelectron spectroscopy and photoelectron circular dichroism (PECD) for the chiral molecule (1R,4R)-3-(heptafluorobutyryl)-(+)-camphor (HFC) and its europium complex Eu(III) tris[3-(heptafluorobutyryl)-(1R,4R)-camphorate] (Eu-HFC$_{3}$), the latter of which constitutes the heaviest organometallic molecule for which PECD has yet been measured. We discuss the role of keto-enol tautomerism in HFC, both as a free molecule and complexed in Eu-HFC$_{3}$. PECD is a uniquely sensitive probe of molecular chirality and structure such as absolute configuration, conformation, isomerisation, and substitution, and as such is in principle well suited to unambiguously resolving tautomers; however modeling remains challenging. For small organic molecules, theory is generally capable of accounting for experimentally measured PECD asymmetries, but significantly poorer agreement is typically achieved for the case of large open-shell systems. Here, we report PECD asymmetries ranging up to $\sim8\%$ for HFC and $\sim7\%$ for Eu-HFC$_{3}$, of similar magnitude to those reported previously for smaller isolated chiral molecules, indicating that PECD remains a practical experimental technique for the study of large, complicated chiral systems.

Spectroscopic techniques that are sensitive to molecular chirality are important analytical tools to quantitatively determine enantiomeric excess and purity of chiral molecular samples. Many chiroptical processes however produce weak enantio-specific asymmetries due to their origin relying on weak magnetic dipole or electric quadrupole effects. Photoelectron circular dichroism (PECD) in contrast, is an intense effect, that is fully contained in the electric dipole description of light matter interaction and creates a chiral asymmetry in the photoelectron angular distribution. Here, we demonstrate that this chiral signature in the angular distribution of emitted electrons can be translated into the total photoionization yield for submicron-sized condensed samples. The resulting chiral asymmetry of the photoionization yield (CAPY), mediated by the attenuation of light within the particles, can be detected experimentally without requiring high vacuum systems and electron spectrometers. This effect can be exploited as an analytical tool with high sensitivity to chirality and enantiopurity for studies of chiral organic and hybrid submicron particles in environmental, biomedical or catalytic applications.

Ultrafast electron microscopy (UEM) has found widespread applications in physics, chemistry, and materials science, enabling real-space imaging of dynamics on ultrafast timescales. Recent advances have pushed the temporal resolution of UEM into the attosecond regime, enabling the attomicroscopy technique to directly visualize electron motion. In this work, we extend the capabilities of this powerful imaging tool to investigate ultrafast electron dynamics in a biological system by imaging and controlling light induced electronic and chemical changes in the conductive network of multicellular cable bacteria. Using electron energy loss spectroscopy (EELS), we first observed a laser induced increase in {\pi}-electron density, accompanied by spectral peak broadening and a blueshift features indicative of enhanced conductivity and structural modification. We also traced the effect of ultrafast laser pumping on bulk plasmon electron oscillations by monitoring changes in the plasmon like resonance peak. Additionally, we visualized laser induced chemical structural changes in cable bacteria in real space. The imaging results revealed carbon enrichment alongside a depletion of nitrogen and oxygen, highlighting the controllability of chemical dynamics. Moreover, time resolved EELS measurements further revealed a picosecond scale decay and recovery of both {\pi}-electron and plasmonic features, attributed to electron phonon coupling. In addition to shedding light on the mechanism of electron motion in cable bacteria, these findings demonstrate ultrafast modulation and switching of conductivity, underscoring their potential as bio-optoelectronic components operating on ultrafast timescales.

We present an experimental demonstration of boson sampling as a hardware accelerator for Monte Carlo integration. Our approach leverages importance sampling to factorize an integrand into a distribution that can be sampled using quantum hardware and a function that can be evaluated classically, enabling hybrid quantum-classical computation. We argue that for certain classes of integrals, this method offers a quantum advantage by efficiently sampling from probability distributions that are hard to simulate classically. We also identify structural criteria that must be satisfied to preserve computational hardness, notably the sensitivity of the classical post-processing function to high-order quantum correlations. To validate our protocol, we implement a proof-of-principle experiment on a programmable photonic platform to compute the first-order energy correction of a three-boson system in a harmonic trap under an Efimov-inspired three-body perturbation. The experimental results are consistent with theoretical predictions and numerical simulations, with deviations explained by photon distinguishability, discretization, and unitary imperfections. Additionally, we provide an error budget quantifying the impact of these same sources of noise. Our work establishes a concrete use case for near-term photonic quantum devices and highlights a viable path toward practical quantum advantage in scientific computing.

Understanding inner-shell decay processes in heavy-element molecules is essential for unraveling x-ray-induced photodynamics and advancing molecular imaging techniques. In this study, we investigate the influence of atomic substitution on core-hole relaxation dynamics and molecular fragmentation in Br2 and IBr, initiated by x-ray absorption at the Br K-edge. Using a combination of X-ray/ion coincidence measurements and Monte Carlo/molecular dynamics simulations, we track charge distribution and the kinetic energy release (KER) of fragment ions with a total charge from 2+ to 8+. For both molecules, the simulated KER values show good agreement with experiment across different fragmentation channels. Our comparison reveals that substituting Br with the heavier I atom in IBr has minimal impact on the inner-shell electronic decay process, but significantly influences nuclear motion, leading to slower dissociation, thereby a KER close to the Coulomb limit, an effect attributed to the atomic mass. These findings highlight the interplay between electronic and nuclear effects in molecular fragmentation, particularly in heavy-element species, and provide new insights into medical therapies, structural biology, and astrophysics.

This paper investigates quantum dots (QDs), which are miniature semiconductor structures with remarkable optical and electrical properties due to quantum confinement processes. Traditional QDs, such as CdTe, have been extensively investigated; however, they frequently exhibit toxicity and stability issues. Graphene quantum dots (GQDs) are emerging as a safer and more stable alternative to traditional QDs. GQDs are honeycomb-lattice carbon atoms with unique electronic and optical properties that make them promising candidates for biomedical, electronic, and energy storage applications. GQD synthesis methods (top-down and bottom-up) and their advantages over standard QDs include better photostability, biocompatibility, and configurable band gaps. GQDs are perfect for real-world uses like sensitive biosensing, real-time food safety monitoring, and smart packaging because of their low toxicity, high sensitivity, and affordability. These uses are all essential for cutting down on food grain waste. This emphasizes the growing significance of GQDs in advancing nanotechnology and their potential integration with quantum technologies, paving the door for creative solutions in biosensing, food safety, environmental monitoring, and future quantum electronics.

$\textit{Ab initio}$ calculations of the parallel component of the magnetic dipole hyperfine structure (HFS) constant have been carried out for hydroxyl radical isotopologues ($^{16,17}$OH(D)) over the internuclear distance range $R \in [0.6, 1.8]$ \r{A}. For the ground electronic state $X^2\Pi$, the HFS functions were evaluated for contributions induced by both oxygen and hydrogen nuclei. In addition, the hydrogen-induced HFS curve was calculated for the excited $A^2\Sigma^+$ state. The quantum-chemistry study employs a four-component relativistic coupled-cluster (CC) method, including excitations up to the triple level, namely: the contribution of triple-cluster amplitudes was studied both perturbatively (CCSD(T)) and through fully iterative calculations (CCSDT). The resulting oxygen- and hydrogen-induced HFS functions represent the most accurate and reliable theoretical predictions to date exhibiting excellent agreement with semiempirical curve for hydrogen-induced HFS derived from high-resolution spectroscopic data for the lowest vibrational levels ($v\in [0,2]$) of the electronic $X^2\Pi$ state. Vibrationally averaged $\textit{ab initio}$ values are consistent with experimental values within $1\%$ for all states considered. Furthermore, the internuclear distance range over which the HFS curves are defined has been extended beyond that of previous studies, thereby providing a robust foundation for accurate HFS treatments of higher-lying rovibrational levels of OH isotopologues within both adiabatic and non-adiabatic frameworks.

Aminoacetonitrile occupies a prime importance in the interface between astrochemistry and prebiotic chemistry. Its detection in the ISM establishes it as part of the organic inventory of star-forming regions, while its role as a glycine precursor highlights its significance for origins-of-life scenarios. In this work, electron scattering from aminoacetonitrile has been studied using the R-matrix method in the low-energy range from 0 to 10 eV. The calculations were carried out within the C_s point group using static-exchange (SE), static-exchange plus polarization (SEP), and configuration interaction (CI) models, with two basis sets (6-311G* and cc-pVTZ). Various scattering observables such as elastic, excitation, momentum transfer, and differential cross sections were examined. Since aminoacetonitrile is a prebiotically relevant molecule, these findings provide valuable insight into electron-driven processes in complex organic systems and form a theoretical foundation for future work on electron-induced reactivity in prebiotic and astrophysical environments.

Ethylene glycol is a prebiotically relevant complex organic molecule detected in interstellar and cometary environments, yet quantitative low-energy electron-ethylene glycol scattering data remain limited for astrochemical modeling. This work presents an R-matrix study of low-energy electron collisions with ethylene glycol over the 0 to 12 eV energy range, using static exchange (SE), static exchange plus polarization (SEP), and configuration interaction (CI) models with 6-311G* and cc-pVTZ basis sets. We compute elastic, excitation, and differential cross sections within a close coupling framework. The dataset offers benchmark inputs for astrochemical models, supporting interpretation of ethylene glycol abundances in space and refining constraints on electron-induced prebiotic pathways.

Machine learned coarse grained (CG) potentials are fast, but degrade over time when simulations reach undersampled biomolecular conformations, and generating widespread all atom (AA) data to combat this is computationally infeasible. We propose a novel active learning framework for CG neural network potentials in molecular dynamics (MD). Building on the CGSchNet model, our method employs root mean squared deviation (RMSD) based frame selection from MD simulations in order to generate data on the fly by querying an oracle during the training of a neural network potential. This framework preserves CG level efficiency while correcting the model at precise, RMSD identified coverage gaps. By training CGSchNet, a coarse grained neural network potential, we empirically show that our framework explores previously unseen configurations and trains the model on unexplored regions of conformational space. Our active learning framework enables a CGSchNet model trained on the Chignolin protein to achieve a 33.05% improvement in the Wasserstein 1 (W1) metric in Time lagged Independent Component Analysis (TICA) space on an in house benchmark suite.

Many-body correlation plays a crucial role in the low-energy positron-molecule scattering dynamics. In the present work, we have integrated a recent model correlation potential, developed by Swann and Gribakin, with the single-center expansion method and verified its efficacy in reproducing the best of ab initio and experimental results, for both non-polar and polar molecules. Starting with the already tested molecules-hydrogen, ethylene, and acetylene with the model correlation, we extended our calculations to oxygen-containing molecules: oxygen, water, and formic acid. In order to provide a comparative study, we have also performed calculations employing the model correlation of Perdew and Zunger. Integral, differential, and momentum transfer cross sections are reported for the target molecules. Positron virtual/bound state formation is also predicted using both of the model correlations. Overall, an improved agreement of our results with the literature for the recent model suggests the approach can be employed for larger systems, where the ab initio techniques are difficult to implement.

High-harmonic spectroscopy (HHS) in liquids promises real-time access to ultrafast electronic dynamics in the native environment of chemical and biological processes. While electron recollision has been established as the dominant mechanism of high-harmonic generation (HHG) in liquids, resolving the underlying electron dynamics has remained elusive. Here we demonstrate attosecond-resolved measurements of recolliding electron wave packets, extending HHS from neat liquids to aqueous solutions. Using phase-controlled two-colour fields, we observe a linear scaling of the two-colour delay that maximizes even-harmonic emission with photon energy, yielding slopes of 208+/-55 as/eV in ethanol and 124+/-42 as/eV in water, the latter matching ab initio simulations (125+/-48 as/eV). In aqueous salt solutions, we uncover interference minima whose appearance depends on solute type and concentration, arising from destructive interference between solute and solvent emission. By measuring the relative phase of solvent and solute HHG, we retrieve a variation of electron transit time by 113+/-32 as/eV, consistent with our neat-liquid results. These findings establish HHS as a powerful attosecond-resolved probe of electron dynamics in disordered media, opening transformative opportunities for studying ultrafast processes such as energy transfer, charge migration, and proton dynamics in liquids and solutions.

Superfluid He nanodroplets resonantly excited by extreme ultraviolet (XUV) pulses exhibit complex relaxation dynamics, including the formation of metastable excited He$^*$ atoms trapped in bubbles, the desorption of excited atoms from the droplet surface, and autoionization via interatomic Coulombic decay (ICD). Irradiation with intense infrared pulses can trigger avalanche ionization, leading to the formation and subsequent expansion of a He nanoplasma. Here, we introduce a novel approach to probe the ICD dynamics over timescales spanning femtoseconds to nanoseconds. Our method exploits the efficient ignition of a nanoplasma through tunnel ionization of excited helium atoms attached to the droplets and the detection of XUV fluorescence emitted from the resulting nanoplasma. Using quantum mechanical and classical calculations, we interpret the nanosecond fluorescence decay as a signature of ICD mediated by He$^*$ freely roaming on the nanodroplet surface.