Dynamical tunneling through a chaotic region

It is shown that a non-vibrating diatomic molecule (i.e. a rigid rotor) in the presence of a strong laser field changes its hindered rotational motion (which on the average is in resonance with the oscillating time dependent field) from anti-clockwise to clockwise (hindered) rotational motion. This transition is classically forbidden and is another example of a quantum mechanical tunneling phenomenon occurring due to the time-reversal symmetry of the Hamiltonian. Classically, the two stable rotational modes are separated by an extended chaotic region in phase space. The Husimi representation of the quasienergy states of the time-periodic quantum system enables us to localize wave packets inside the classical stability islands. The effect of the field and the molecular parameters on the perioid of this oscillation is obtained from the quasienergy splittings without the need to carry out long time dependent computations. An analytical analysis of the dynamical tunneling using an extended version of the (t,t) formalism recently developed (J. Chem. Phys.99, 4590 (1993)) is in remarkable agreement with the numerical results.Member of the Minerva center of non-linear physics of complex systems at the Technion     

Chimera Spectrum Diagnostics for Peptides Using Two-Dimensional Partial Covariance Mass Spectrometry

The rate of successful identification of peptide sequences by tandem mass spectrometry (MS/MS) is adversely affected by the common occurrence of co-isolation and co-fragmentation of two or more isobaric or isomeric parent ions. This results in so-called `chimera spectra’, which feature peaks of the fragment ions from more than a single precursor ion. The totality of the fragment ion peaks in chimera spectra cannot be assigned to a single peptide sequence, which contradicts a fundamental assumption of the standard automated MS/MS spectra analysis tools, such as protein database search engines. This calls for a diagnostic method able to identify chimera spectra to single out the cases where this assumption is not valid. Here, we demonstrate that, within the recently developed two-dimensional partial covariance mass spectrometry (2D-PC-MS), it is possible to reliably identify chimera spectra directly from the two-dimensional fragment ion spectrum, irrespective of whether the co-isolated peptide ions are isobaric up to a finite mass accuracy or isomeric. We introduce ‘3-57 chimera tag’ technique for chimera spectrum diagnostics based on 2D-PC-MS and perform numerical simulations to examine its efficiency. We experimentally demonstrate the detection of a mixture of two isomeric parent ions, even under conditions when one isomeric peptide is at one five-hundredth of the molar concentration of the second isomer.     

Ab initio interatomic decay widths of excited states by applying Stieltjes imaging to Lanczos pseudospectra

Electronically excited states of atoms and molecules in an environment may decay in interatomic processes by transferring excess energy to neighboring species and ionizing them. The corresponding interatomic decay width is the most important characteristic of the decay allowing to calculate its efficiency and the final states' distribution. In this paper we present calculations of interatomic widths by the Fano-Stieltjes method applied to Lanczos pseudospectra, which has been previously shown to provide accurate autoionization widths in atoms and molecules. The use of Lanczos pseudospectra allows one to avoid the full diagonalization bottleneck and makes the method applicable to larger systems. We apply the present method to the calculation of interatomic decay widths in NeMg, NeAr and HCN[middle dot]Mg(n), n = 1, 2 clusters. The results are compared with widths obtained analytically and by other ab initio methods where available.     

Duality between differentiability and rotundity for convex functions

We generalize a theorem of Asplund and Rockafellar concerning the duality between the differentiability of a convex function with respect to a system of setsA and theA rotundity of the conjugate convex function to the case of differentiabilities and rotundities defined by pseudotopologies of a broad class, including pseudotopologies of convergence on systems of filters and their bulblike modifications.     

Decay rates of inner-valence excitations in noble gas atoms

A Fano - algebraic diagrammatic construction - Stieltjes method has been recently developed for ab initio calculations of nonradiative decay rates [V. Averbukh and L. S. Cederbaum, J. Chem. Phys. 123, 204107 (2005)] of singly ionized states. In the present work this method is generalized for the case of electronic decay of excited states. The decay widths of autoionizing inner-valence-excited states of Ne, Ar, and Kr are calculated. Apart from the lowest excitation of Kr, they are found to be in good to excellent agreement with the experimental values. Comparison with the other theoretical studies shows that in many cases the new method performs better than the previously available techniques.