arXiv subjects

Michael Baer

Publications and source records attributed to Michael Baer.

9 recordsLinked to original sources

arXiv2024

Quasi-classical Trajectory Calculations on a Two-state Potential Energy Surface Including Nonadiabatic Coupling Terms as Friction for D+ + H2 Collisions

Akin to the traditional quasi-classical trajectory method for investigating the dynamics on a single adiabatic potential energy surface for an elementary chemical reaction, we carry out the dynamics on a 2-state ab initio potential energy surface including nonadiabatic coupling terms as friction terms for D+ + H2 collisions. It is shown that the resulting dynamics correctly accounts for nonreactive charge transfer, reactive non charge transfer and reactive charge transfer processes. In addition, it leads to the formation of triatomic DH2+ species as well.

physics.chem-ph↗

arXiv2023

Non-adiabatic coupling as friction in the formation of H3+: A classical mechanical study

By going beyond the Born-Oppenheimer approximation and treating the non-adiabatic coupling terms (NACTs) as equivalent to a frictional force in a molecular system, the classical equations of motion are solved for a test case of H3+. Using an ab initio potential energy surface for the ground electronic state and its NACTs with the first excited state of H3+, it is shown that (D+, H2) collisions are slowed enough to result in trapping and formation of a stable DH2+.

physics.chem-ph↗

arXiv2019

Topological Studies related to Molecular Systems formed soon after the Big Bang: HeH2+ as the Precursor for HeH+

In the early universe, following the nucleosynthesis, conditions were right for recombination processes to take place yielding neutral atoms H, He and Li. The understanding so far in astrophysics is that the first molecule to be formed was HeH+ by radiative association (He + H+ -> HeH+ + h(nu) and He+ + H -> HeH+ + h(nu). The recent report by Guesten et al (Nature, 568, 357, 2019) of detection of HeH+ in planetary Nebula NGC 7027 confirms its presence, but it does not conclusively prove the origin of this species. To create molecules from free moving quasi-ions surrounded by an electronic cloud, the Born-Oppenheimer-Huang (BOH) theory furnishes two kinds of forces, namely, one that results from the Potential Energy Surfaces (PESs) and the other from Non-Adiabatic Coupling Terms (NACTs). Whereas the PESs are known to manage slow moving quasi-ions the NACTs, with their, frequently, infinitely large values at the vicinity of the singularities can control the fast moving quasi-ions. To achieve that the BOH equation indicates that the NACTs are affecting the fast moving quasi-ions directly and if they are attributed with dissipative features or in other words to behave as a Friction Force they indeed could serve (like any other ordinary friction) as moderators for the fast atomic(ionic) species. It is proposed in the present paper that the triatomic HeH2+ was the precursor to HeH+ and it could have been formed by the (He, H, H)+ nuclei coming together under the electron cloud, facilitated by the NACTs between different electronic states acting as an astronomical friction force. This is possible because of the singularities in the NACTs for triatomic systems and NOT for diatomic systems. Although the existence of HeH2+ was established in the laboratory in 1996, it has not been detected in the interstellar media so far. But, there is no reason why it cannot be detected in near future.

physics.chem-ph↗

arXiv2018

Topological Study of the $H_3^{++}$ Molecular System: $H_3^{++}$ as a Cornerstone for Building Molecules during the Big Bang

The present study is devoted to the possibility that tri-atomic molecules were formed during or shortly after the Big Bang. For this purpose we consider the ordinary $H_3^{+}$ and $H_3$ and the primitive tri-atomic molecular system, $H_3^{++}$, which, as is shown, behaves differently. The study is carried out by comparing the topological features of these systems as they are reflected through their non-adiabatic coupling terms. Although the $H_3^{++}$ is not known to exist as a molecule, we found that it behaves as such at intermediate distances. However this illusion breaks down as its asymptotic region is reached. Our study indicates that whereas $H_3^{+}$ and $H_3$ dissociate smoothly, the $H_3^{++}$, does not seem to do so. Nevertheless, the fact that $H_3^{++}$ is capable of living as a molecule on borrowed time enables it to catch an electron and form a molecule via the reaction $H_3^{++} + e \to H_3^{+}$ that may dissociate properly: $H_3^{+} \to H^{+} + H_2$ or $H + H_2^+$. Thus, the two unique features acquired by $H_3^{++}$ namely, that it is the most primitive system formed by three protons and one electron and topologically, still remain for an instant a molecule, may make it the sole candidate for becoming the \bold{cornerstone} for creating the molecules.

physics.chem-ph↗

arXiv2017

Introducing Time-dependent Molecular Fields: Derivation of the Wave Equations

This article is part of a series of articles trying to establish the concept Molecular Field. The theory that induced us to introduce this novel concept is based on the Born-Huang expansion as applied to the Schroedinger equation that describes the interaction of a molecular system with an external electric field. Assuming the molecular system is made up of two coupled adiabatic states the theory leads from a single spatial Curl Equation, two space-time Curl equations and one single space-time Divergent equation to a pair of decoupled Wave Equations usually encountered within the theory of fields. In the present study the Wave Equations are derived for an external field having two features: (a) its intensity is high enough; (b) its duration is short enough. For this situation the study reveals that the just described interaction creates two fields that coexist within a molecule: one is a novel vectorial field formed via the interaction of the external field with the Born-Huang non-adiabatic coupling terms (NACT) and the other is an ordinary, scalar, electric field essentially identical to the original external field. Part of the present study is devoted to the visualization of the outcomes via two intersecting Jahn-Teller cones which contain NACTs that become singular at their intersection point, also known as the point of Conical Intersection. This description is reminiscent of a metaphoric cosmic Black-Hole which swallows one type of an electric field and creates a new type. Finally, the fact that eventually we are facing a kind of a cosmic situation may bring us to speculate that singular NACTs are a result of cosmic phenomena. Thus, if indeed this singularity is somehow connected to reality then, like other singularities in physics, it is formed at (or immediately after) the Big Bang (and because of that, eventually the ability to form molecules).

physics.chem-ph↗

arXiv2017

The Special Theory of Relativity as Applied to the Born-Oppenheimer-Huang Approach

In two recent publications ( Int. J. Quant. Chem. 114, 1645 (2014) and Molec. Phys. 114, 227 (2016)) it was shown that the Born -Hwang (BH) treatment of a molecular system perturbed by an external field yields a set of decoupled vectorial Wave Equations, just like in Electromagnetism. This finding led us to declare on the existence of a new type of Fields, which were termed Molecular Fields. The fact that such fields exist implies that at the vicinity of conical intersections exist a mechanism that transforms a passing-by electric beam into a field which differs from the original electric field. This situation is reminiscent of what is encountered in astronomy where Black Holes formed by massive stars may affect the nature of a near-by beam of light. Thus if the NonAdiabatic-Coupling-Terms (NACT) with their singular points may affect the nature of such a beam (see the above two publications) then it would be interesting to know to what extend NACTs (and consequently also the BH equation) will be affected by the special theory of relativity as introduced by Dirac. Indeed while applying the Dirac approach we derived the relativistic affected NACTs as well as the corresponding BH equation.

physics.chem-ph↗

arXiv2008

Tight Bounds on Minimum Maximum Pointwise Redundancy

This paper presents new lower and upper bounds for the optimal compression of binary prefix codes in terms of the most probable input symbol, where compression efficiency is determined by the nonlinear codeword length objective of minimizing maximum pointwise redundancy. This objective relates to both universal modeling and Shannon coding, and these bounds are tight throughout the interval. The upper bounds also apply to a related objective, that of dth exponential redundancy.

cs.IT↗

arXiv2007

Conical intersections induced by the Renner effect in polyatomic molecules

Characterizing and localizing electronic energy degeneracies is important for describ-ing and controlling electronic energy flow in molecules. We show, using topological phase considerations that the Renner effect in polyatomic molecules with more than 3 nuclei is necessarily accompanied by 'satellite' conical intersections. In these intersections the non-adiabatic coupling term is on the average half an integer. We present ab-inito results on the tetra-atomic radical cation C2H2+ to demonstrate the theory

cond-mat.mtrl-sci↗

arXiv1995

Calculation of the Density of States Using Discrete Variable Representation and Toeplitz Matrices

A direct and exact method for calculating the density of states for systems with localized potentials is presented. The method is based on explicit inversion of the operator $E-H$. The operator is written in the discrete variable representation of the Hamiltonian, and the Toeplitz property of the asymptotic part of the obtained {\it infinite} matrix is used. Thus, the problem is reduced to the inversion of a {\it finite} matrix.

cond-mat↗