arXiv subjects

P. Kowalczyk

Publications and source records attributed to P. Kowalczyk.

9 recordsLinked to original sources

arXiv2025

The C$^1Π_{\mathrm{u}}$ state of potassium dimer revisited: an~extensive study by polarisation labelling spectroscopy method

The polarisation labelling spectroscopy technique was applied to study the C$^1Π_{\mathrm{u}}$ $\leftarrow$ X$^1Σ^{+}_{\mathrm{g}}$ band system in potassium dimer. About 1100 new rotationally resolved molecular lines were measured in the $22100-24100$~cm$^{-1}$ spectral range. Perturbations of the lowest vibrational levels of the C state were localised and their origin discussed. A set of Dunham coefficients was deduced to fit the unperturbed levels of the C$^1Π_{\mathrm{u}}$ state with $0 \le v \le 38$ and $18 \le J \le 101$ and the potential energy curve of the state was constructed.

physics.atom-ph↗

arXiv2025

The double minimum E(3)$^1Σ^{+}_{\mathrm{u}}$ state in Cs$_2$

The double minimum E$^1Σ^{+}_{\mathrm{u}}$ state in caesium dimer was investigated by analysing spectra of the E$^1Σ^{+}_{\mathrm{u}}$ $\leftarrow$ X$^1Σ^{+}_{\mathrm{g}}$ band system, simplified by polarisation labelling. A total of 6727 rotationally resolved transitions to levels situated in the inner well and above the internal barrier were identified and a potential energy curve allowing to reproduce their energies was constructed using the Fourier grid Hamiltonian and inverted perturbation approach methods. The unambiguousness of the potential curve in view of lack of data related to levels located in the outer well is discussed.

physics.atom-ph↗

arXiv2016

A novel route to a Hopf-bifurcation scenario in switched systems with dead zone

Planar switched system with dead-zone are analyzed. In particular, we consider the effects of perturbation of the linear control law from purely positional to position-velocity control. This type of perturbation leads to a novel Hopf-like discontinuity induced bifurcation. We show that this bifurcation leads to the creation of small scale limit cycle attractors, which scale as the square root of the bifurcation parameter. We note that a Hopf-like bifurcation analyzed in non-smooth systems is characterized by a linear scaling law. We then investigate numerically a planar switched system with positional feedback law, dead-zone and time delay in the switching function. Using the same parameter values as for the switched system without delay in the switching function, we show numerically a Hopf-like bifurcation scenario which matches qualitatively and quantitatively with the scenario analyzed for the non-delayed system.

nlin.CD↗

arXiv2016

Gyroidal nanoporous carbons - Adsorption and separation properties explored using computer simulations

Adsorption and separation properties of gyroidal nanoporous carbons (GNCs) - a new class of exotic nanocarbon materials are studied for the first time using hyper parallel tempering Monte Carlo Simulation technique. Porous structure of GNC models is evaluated by the method proposed by Bhattacharya and Gubbins. All the studied structures are strictly microporous. Next, mechanisms of Ar adsorption are described basing on the analysis of adsorption isotherms, enthalpy plots, the values of Henry's constants, $α_{s}$ and adsorption potential distribution plots. It is concluded that below pore diameters ca. 0.8 nm, primary micropore filling process dominates. For structures possessing larger micropores, primary and secondary micropore filling mechanism is observed. Finally, the separation properties of GNC toward CO$_2$/CH$_4$, CO$_2$/N$_2$, and CH$_4$/N$_2$ mixtures are discussed and compared with separation properties of Virtual Porous Carbon models. GNCs may be considered as potential adsorbents for gas mixture separation, having separation efficiency similar or even higher than activated carbons with similar diameters of pores.

cond-mat.mes-hall↗

arXiv2011

Equilibrium Clusters in Concentrated Lysozyme Protein Solutions

We have studied the structure of salt-free lysozyme at 293 K and pH 7.8 using molecular simulations and experimental SAXS effective potentials between proteins at three volume fractions, 0.012, 0.033, and 0.12. We found that the structure of lysozyme near physiological conditions strongly depends on the volume fraction of proteins. The studied lysozyme solutions are dominated by monomers only for <0.012; for the strong dilution 70% of proteins are in a form of monomers. For 0.033 only 20% of proteins do not belong to a cluster. The clusters are mainly elongated. For 0.12 almost no individual particles exits, and branched, irregular clusters of large extent appear. Our simulation study provides new insight into the formation of equilibrium clusters in charged protein solutions near physiological conditions.

cond-mat.soft↗

arXiv2009

On the B^1Πstate of NaCs

The B^1Π<- X^1Σ^+ system of NaCs molecule is investigated experimentally by polarization labelling spectroscopy technique. The inverted perturbation approach method is used to construct the potential energy curve of the B^1Πstate, providing accurate eigenenergies for vibrational levels v = 0 - 15.

physics.chem-ph↗

arXiv2008

Mono-, bi- and tri- graphene layers deposited on conductive Au/Cr/SiO2/Si substrate studied by scanning tunnelling spectroscopy

Graphene devices require electric contacts with metals, particularly with gold. Scanning tunneling spectroscopy studies of electron local density of states performed on mono-, bi- and tri- graphene layer deposited on metallic conductive Au/Cr/SiO2/Si substrate shows that gold substrate causes the Fermi level shift downwards which means that holes are donated by metal substrate to graphene which becomes p-type doped. These experimental results are in good accordance with recently published density function theory calculations. The estimated positions of the Dirac point show that the higher number of graphene layers the lower Fermi level shift is observed.

cond-mat.mtrl-sci↗

arXiv2008

Dynamics of symmetric dynamical systems with delayed switching

We study dynamical systems that switch between two different vector fields depending on a discrete variable and with a delay. When the delay reaches a problem-dependent critical value so-called event collisions occur. This paper classifies and analyzes event collisions, a special type of discontinuity induced bifurcations, for periodic orbits. Our focus is on event collisions of symmetric periodic orbits in systems with full reflection symmetry, a symmetry that is prevalent in applications. We derive an implicit expression for the Poincare map near the colliding periodic orbit. The Poincare map is piecewise smooth, finite-dimensional, and changes the dimension of its image at the collision. In the second part of the paper we apply this general result to the class of unstable linear single-degree-of-freedom oscillators where we detect and continue numerically collisions of invariant tori. Moreover, we observe that attracting closed invariant polygons emerge at the torus collision.

math.DS↗

arXiv2004

A regularized inverted perturbation approach method: potential energy curve of the $4^1Σ^+_u$ state in $Na_2$

We describe a modification of the inverted perturbation approach method allowing to construct physically sensible potential energy curves for electronic states of diatomic molecules even when some parts of the potential are not adequately characterized by the experimental data. The method is based on a simple regularization procedure, imposing an additional constraint on the constructed potential curve. In the present work it is applied to the double minimum 4$^1Σ^{+}_{\mathrm u}$ state of Na$_2$, observed experimentally by polarization labeling spectroscopy technique.

physics.atom-ph↗