arXiv subjects

Idan Haritan

Publications and source records attributed to Idan Haritan.

7 recordsLinked to original sources

arXiv2026

Do Water Molecules Always Stabilize Resonances? Microhydration Effects on Thymine Shape Resonances

We investigate microhydration effects on the three low-lying {\pi}* shape resonances of thymine using the Resonance via Pad\'e approach in combination with the DLPNO-EA-EOM-CCSD method. For isolated thymine, the calculated resonance positions are benchmarked against projected CAP-EA-EOM-CCSD calculations and compared with available theoretical and experimental data. Upon hydration, the 1{\pi}* and 2{\pi}* resonances undergo systematic stabilization accompanied by significant increases in their lifetimes, whereas the 3{\pi}* resonance exhibits a more complex behavior. In particular, the lifetime of the lowest resonance increases from 39 fs in isolated thymine to 110 fs in the thymine(H2O)3 cluster. Detailed analysis reveals that the observed resonance shifts arise from competing contributions involving hydrogen bonding, electrostatic interactions, microsolvation-induced geometric distortion, and finite-basis-set effects. Ghost-atom calculations demonstrate that diffuse basis functions associated with nearby water molecules contribute appreciably to the apparent stabilization, while explicit inclusion of water molecules leads to genuine physical stabilization of the resonance states. Furthermore, calculations on multiple conformers of the monohydrated cluster show that resonance positions and lifetimes depend strongly on the local hydrogen-bonding arrangement and microsolvation geometry. These findings demonstrate that resonance stabilization in microhydrated nucleobases is governed by a subtle interplay between geometry, basis-set effects, and intermolecular interactions.

physics.chem-ph↗

arXiv2026

The Effect of Base-Pairing on the Shape Resonances of Nucleobases

In this work, we have studied the effect of base-pairing on the shape resonances of guanine and cytosine nucleobases. Among the seven {\pi}* resonances we identified in the guanine-cytosine (GC) anion radical, three were centered on cytosine, and the remaining were guanine-centered. Relative to the isolated bases, upon base pair formation, the cytosine resonances were red shifted, while the guanine-centered states showed an opposite trend - where their energy was blue shifted. In addition to the electronic interactions, geometric distortion and basis set superposition error plays a crucial role in the resonance positions and widths of the GC radical anion. The electronic interaction from the complementary base seems to have a larger effect on the stabilization of the anionic resonances than the surrounding environment.

physics.chem-ph↗

arXiv2025

The Effect of Aqueous Medium on Nucleobase Shape Resonances: Insights from Microsolvation

We have studied the effect of microhydration on the shape resonances of uracil nucleobase. The resonance parameters were determined using the resonance via Pad\'e approach along with the efficient wave function-based EA-EOM-DLPNO-CCSD method. Our results showed that the uracil resonances become stabilized with an increase in the extent of microsolvation. The energy of the resonances decreased, and the lifetime increased as the number of water molecules surrounding uracil was increased. It showed that ten water molecules are sufficient to make the lowest shape resonance of uracil a bound radical anionic state. Our results also indicate that the lowest energy resonance state may become a bound state under bulk solvation.

physics.chem-ph↗

arXiv2025

Effect of Protein Environment on the Shape Resonances of RNA Nucleobases: Insights From a Model System

In this work, the effect of amino acid environment on the nucleobase-centered anion radical shape resonances is investigated by employing uracil as a model system for pyrimidine base in RNA. Anionic uracil-glycine complexes have been used to model the RNA-protein interactions. The resonance positions and widths of these complexes have been simulated using the equation of motion coupled cluster method coupled with resonance via Pad\'e approach. Our work shows that in the transient negative ion (TNI, or, the anion radical of glycine:uracil complex), glycine stabilizes the nucleobase-centered resonances through hydrogen bonding, increasing the lifetime of TNI. At the same time, a glycine-centered resonance shows the ability of amino acids to capture the electron density and move it away from the uracil nucleobase. At the micro-solvation level, this modeling indicates that amino acids would have more influence on nucleobase-centered resonances in the TNI than that displayed by the corresponding aqueous environment.

physics.chem-ph↗

arXiv2025

An Efficient scaled opposite-spin MP2 method for periodic systems

We develop SOS-RILT-MP2, an efficient Gaussian-based periodic scaled opposite-spin second-order M{\o}ller-Plesset perturbation theory (SOS-MP2) algorithm that utilizes the resolution-of-the-identity approximation (RI) combined with the Laplace transform technique (LT). In our previous work [J. Chem. Phys. 157, 174112 (2022)], we showed that SOS-MP2 yields better predictions of the lattice constant, bulk modulus, and cohesive energy of 12 simple semiconductors and insulators compared to conventional MP2 and some of the leading density functionals. In this work, we present an efficient SOS-MP2 algorithm that has a scaling of O(N4) with the number of atoms N in the unit cell and a reduced scaling with the number of k-points in the Brillouin zone. We implemented and tested our algorithm on both molecular and solid-state systems, confirming the predicted scaling behavior by systematically increasing the number of atoms, the size of the basis set, and the density of k-point sampling. Using the benzene molecular crystal as a case study, we demonstrated that SOS-RILT-MP2 achieves significantly improved efficiency compared to conventional MP2. This efficient algorithm can be used in the future to study complex materials with large unit cells as well as defect structures.

physics.chem-ph↗

arXiv2018

Resonance poles and threshold energies for hadron physical problems by a model-independent universal algorithm

We show how complex resonance poles and threshold energies for systems in hadron physics can be accurately obtained by using a method based on the Padé-approximant which was recently developed for the calculation of resonance poles for atomic and molecular auto-ionization systems. The main advantage of this method is the ability to calculate the resonance poles and threshold energies from \emph{real} spectral data. In order to demonstrate the capabilities of this method we apply it here to an analytical model as well as to experimental data for the squared modulus of the vector pion form factor, the S0 partial wave amplitude for $ππ$ scattering and the cross section ratio $R(s)$ for $e^+e^-$ collisions. The extracted values for the resonance poles of the $ρ(770)$ and the $f_0(500)$ or $σ$ meson are in very good agreement with the literature. When the data are noisy the prediction of decay thresholds proves to be less accurate but feasible.

hep-ph↗

arXiv2015

Atomic and molecular complex resonances from real eigenvalues using standard (hermitian) electronic structure calculations

Complex eigenvalues, resonances, play an important role in large variety of fields in physics and chemistry. For example, in cold molecular collision experiments and electron scattering experiments, autoionizing and pre-dissociative metastable resonances are generated. However, the computation of complex resonance eigenvalues is difficult, since it requires severe modifications of standard electronic structure codes and methods. Here we show how resonance eigenvalues, positions and widths, can be calculated using the standard, widely used, electronic-structure packages. Our method enables the calculations of the complex resonance eigenvalues by using analytical continuation procedures (such as Padé). The key point in our approach is the existence of narrow analytical passages from the real axis to the complex energy plane. In fact, the existence of these analytical passages relies on using finite basis sets. These passages become narrower as the basis set becomes more complete, whereas in the exact limit, these passages to the complex plane are closed. As illustrative numerical examples we calculated the autoionization resonances of helium, hydrogen anion and hydrogen molecule. We show that our results are in an excellent agreement with the results obtained by other theoretical methods and with available experimental results.

quant-ph↗