Biomedical subjects

N Moiseyev

Publications and source records attributed to N Moiseyev.

At least 19 recordsLinked to original sources

PubMed2006

On the unphysical impact of complex absorbing potentials on the Hamiltonian and its remedy.

The introduction of complex absorbing potentials as numerical tools to stabilize or increase the efficiency of calculations based on wave-packet propagation or on eigenvalue problems has the drawback of causing a modification of the Hamilton operator of the problem. In this work the consequences of such a modification are analyzed and the corrections required in order to properly describe the original physical process are derived. As an example, the decay of excited molecular states is considered: it is shown that the standard time-independent expression for the decay spectrum loses its validity when a complex absorbing potential is introduced in the nuclear Hamilton operator of the problem. To remedy the situation, a new, very stable formula is derived and tested on relevant model studies. Numerical examples are discussed.

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PubMed2004

On the interatomic Coulombic decay in the Ne dimer.

The interatomic Coulombic decay (ICD) in the Ne dimer is discussed in view of the recent experimental results. The ICD electron spectrum and the kinetic energy release of the Ne+ fragments resulting after Coulomb explosion of Ne2 (2+) are computed and compared to the measured ones. A very good agreement is found, confirming the dynamics predicted for this decay mechanism. The effect of the temperature on the electron spectrum is briefly investigated.

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PubMed2004

Non-Hermitian quantum mechanics: wave packet propagation on autoionizing potential energy surfaces.

The correspondence between the time-dependent and time-independent molecular dynamic formalisms is shown for autoionizing processes. We demonstrate that the definition of the inner product in non-Hermitian quantum mechanics plays a key role in the proof. When the final state of the process is dissociative, it is technically favorable to introduce a complex absorbing potential into the calculations. The conditions which this potential should fulfill are briefly discussed. An illustrative numerical example is presented involving three potential energy surfaces.

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PubMed2001

Non-Hermitian delocalization from Hermitian Hamiltonians.

Here we show that using Galilean transformations the non-Hermitian delocalization phenomenon, which is relevant in different fields, such as bacteria population (e.g., Bacillus subtilis), vortex pinning in superconductors, and stability solutions of hydrodynamical problems discovered by Hatano and Nelson [Phys. Rev. Lett. 77, 5706 (1996)], can be obtained from solutions of the time-dependent Schrödinger equation with a Hermitian Hamiltonian. Using our approach, one avoids the numerical complications and instabilities which result form the calculations of left and right eigenfunctions of the non-Hermitian Hamiltonian which are associated with the non-Hermitian delocalization phenomenon. One also avoids the need to replace the non-Hermitian Hamiltonian H by a supermatrix with twice the dimension of H, where the complex frequencies serve as variational parameters rather than eigenvalues of H.

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PubMed2000

High harmonic generation of soft X-rays by carbon nanotubes

We extend the method for the formulation of selection rules for high harmonic generation spectra [Phys. Rev. Lett. 80, 3743 (1998)] beyond the dipole approximation and apply it to single-walled carbon nanotubes interacting with a circularly polarized laser field. Our results show that the carbon nanotubes can be excellent systems for a selective generation of high harmonics, up to the soft x-ray regime.

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PubMed2000

Interatomic coulombic decay in van der waals clusters and impact of nuclear motion

It is demonstrated that excited van der Waals systems can relax by electron emission via a novel interatomic mechanism. The process is analyzed by means of extensive ab initio calculations of potential energy surfaces and electronic decay rates. The electronic emission, taking place on the same time scale as the motion of the atomic nuclei, is accompanied by interesting dynamical effects amenable to experimental observations. These effects arise as a consequence of the weak chemical bond in van der Waals clusters and the Coulomb repulsion pattern originating from electron emission.

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PubMed2000

Trapping of an electron due to molecular vibrations

Here we first show that the nuclear motion of H-2 generates a continuum of autoionization resonance states. The interference between them increases the lifetime of the trapped electron in the e(-)/H(2) scattering experiments and leads to asymmetric oscillations in the phase of the excitation probability amplitude. This collective coherent interference resonance phenomenon is very different from any known mechanism in quantum mechanics which reveals the fingerprints of overlapping resonances in scattering cross section and results from the non-Hermitian properties of the H-2 Hamiltonian.

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PubMed1995