If we assume that the strong interactions of baryons
and mesons are correctly described in terms of
the broken "eightfold way", we are tempted to
look for some fundamental explanation of the situation.
A highly promised approach is the purely dynamical
"bootstrap" model for all the strongly interacting
particles within which one may try to derive
isotopic spin and strangeness conservation and
broken eightfold symmetry from self-consistency
alone. Of course, with only strong interactions,
the orientation of the asymmetry in the unitary
space cannot be specified; one hopes that in some
way the selection of specific components of the F-spin
by electromagnetism and the weak interactions
determines the choice of isotopic spin and hypercharge
directions.

A Schematic Model of Baryons and Mesons

We review our development on beyond Born–Oppenheimer (BBO) theory and its implementation on various models and realistic molecular processes as carried out over the last 15 years. The theoretical f...

Beyond Born–Oppenheimer theory for spectroscopic and scattering processes

Diabatic states have a long history in chemistry, beginning with early valence bond pictures of molecular bonding and extending through the construction of model potential energy surfaces to the modern proliferation of methods for computing these elusive states. In this review, we summarize the basic principles that define the diabatic basis and demonstrate how they can be applied in the specific context of constrained density functional theory. Using illustrative examples from electron transfer and chemical reactions, we show how the diabatic picture can be used to extract qualitative insight and quantitative predictions about energy landscapes. The review closes with a brief summary of the challenges and prospects for the further application of diabatic states in chemistry.

The diabatic picture of electron transfer, reaction barriers and molecular dynamics

A beyond Born-Oppenheimer treatment of five state molecular system NO3 and the photodetachment spectra of its anion

We present explicit form of Adiabatic to Diabatic Transformation (ADT) equations and expressions of non-adiabatic coupling terms (NACTs) for a coupled five-state electronic manifold in terms of ADT angles between electronic wave functions. ADT matrices eliminate the numerical instability arising from singularity of NACTs and transform the adiabatic Schrodinger equation to its diabatic form. Two real molecular systems NO3 and C6H6+ (Bz+) are selectively chosen for the demonstration of workability of those equations. We examine the NACTs among the lowest five electronic states of the NO3 radical [X2A2′ (12B2), A2E″ (12A2 and 12B1) and B2E′ (12A1 and 22B2)], in which all types of non-adiabatic interactions, that is, Jahn–Teller (JT) interactions, Pseudo Jahn–Teller (PJT) interactions, and accidental conical intersections (CIs) are present. On the other hand, lowest five electronic states of Bz+ [X2E1g (12B3g and 12B2g), B2E2g (12Ag and 12B1g), and C2A2u (12B1u)] depict similar kind of complex feature of...

Five Electronic State Beyond Born–Oppenheimer Equations and Their Applications to Nitrate and Benzene Radical Cation

In order to explore spectroscopic properties of a floppy molecule, it is necessary to compute accurate diabatic potential energy surfaces (PESs) around the Franck–Condon region of nuclear configuration space. In such cases, it is desirable to include the non-adiabatic coupling terms (NACTs) through Jahn–Teller (JT) and pseudo Jahn–Teller (PJT) effects as well as other accidental conical intersections (CIs) prevailing among the electronic states of the molecule. In this work, we investigate NACTs among the five lowest doublet electronic states of NO3 radical [ and 22B2)], in which all those effects (JT, PJT and CIs) have prominent contributions. The study is carried out in terms of normal modes (Qis) of NO3 and the CIs (JT and accidental) are located in a plane of nuclear configuration space of two such coordinates (Qi and Qj). We have calculated ab initio adiabatic PESs and NACTs of those five states of NO3 at the MRCI level as functions of pairwise Qis. Further, to explore the nature of a given C...

K. R. Shamasundar

Papers

A beyond Born-Oppenheimer treatment of five state molecular system NO3 and the photodetachment spectra of its anion

An ab initio investigation of non-adiabatic couplings and conical intersections among the lowest five electronic states of the NO3 radical

Topological studies related to molecular systems formed during the Big Bang: H3+ as an example