While a wealth of studies exist on the potential energy surface (PES) for the F + H2 reaction, exploration of the effect of conical intersections (CIs on the corresponding adiabatic PES has only been initiated. In this respect, a recent emphasis on the specific role of the Jahn-Teller (JT) CI between the two lowest states has shown that the adiabatic-to-diabatic transformation (ADT) angle (mixing angle), γ12, between these two states deviates largely from its quantized value of π for configuration spaces with F close to the H-H system. Hence, investigating the effect of the other CIs present, involving the higher states, on the reactive channel is necessary. In this article, we report for the first time the collinear (2, 3), (3, 4) and (4, 5) JT CIs in this system and also reveal their major effects on γ12, which is instrumental in the diabatization of the PES for the title reaction system. © 2012 Elsevier B.V. All rights reserved.

DEBASIS MUKHOPADHYAY

Chemistry

A DAS

University of Calcutta (informally known as Calcutta University or CU) is a collegiate public state university located in Kolkata, West Bengal, India.&nbsp;Within India it is recognized as a &quot;Five-Star University&quot; and accredited &quot;A&quot; Grade by National Assessment and Accreditation Council.

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The University of Calcutta has secured the Fifth position among the Universities of India in the prestigious &quot;Indian University Ranking 2019&quot; list, released by the NIRF of the Ministry of Human Resource Development, Government of India.

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It was established on 24 January 1857, and was one of the first institutions in Asia to be established as a multidisciplinary and Western-style university. Its alumni and faculty include several heads of state, heads of government, social reformers, prominent artists, only academy award winner and Dirac medal winner in India, many Fellows of the Royal Society and five Nobel laureates as of 2019 which is highest in South Asia.

University Of Calcutta

Chemical Physics

We follow a suggestion by Lipoff and Herschbach Mol. Phys. 108, 1133 (2010)10.1080/00268971003662912 and compare dressed and bare adiabatic potentials to get insight regarding the low-energy dynamics (e.g., cold reaction) taking place in molecular systems. In this particular case, we are interested to study the effect of conical intersections (ci) on the interacting atoms. For this purpose, we consider vibrational dressed adiabatic and vibrational dressed diabatic potentials in the entrance channel of reactive systems. According to our study, the most one should expect, in case of F H 2, is a mild effect of the (1, 2) ci on its reactiveexchange process-an outcome also supported by experiment. This happens although the corresponding dressed and bare potential barriers (and the corresponding van der Waals potential wells) differ significantly from each other. © 2012 American Institute of Physics.

Fulltext

Journal of Chemical Physics

Dressed adiabatic and diabatic potentials to study conical intersections for F + H 2

The approach to calculate improved, two-state, adiabatic-to-diabatic transformation angles (also known as mixing angles), presented before (see Das et al., J Chem Phys 2010, 133, 084107), was used here while studying the F + H 2 system. However, this study is characterized by two new features: (a) it is the first of its kind in which is studied the interplay between Renner-Teller (RT) and Jahn-Teller (JT) nonadiabatic coupling terms (NACT); (b) it is the first of its kind in which is reported the effect of an upper singular RT-NACT on a lower two-state (JT) mixing angle. The fact that the upper NACT is singular (it is shown to be a quasi-Dirac δ-function) enables a semi-analytical solution for this perturbed mixing angle. The present treatment, performed for the F + H 2 system, revealed the existence of a novel parameter, η, the Jahn-Renner coupling parameter (JRCP), which yields, in an unambiguous way, the right intensity of the RT coupling (as resembled, in this case, by the quasi-Dirac δ-function) responsible for the fact that the final end-of-the contour angle (identified with the Berry phase) is properly quantized. This study implies that the numerical value of this parameter is a pure number (independent of the molecular system): η = 2√2/π (= 0.9003) and that there is a good possibility that this value is a novel characteristic molecular constant for a certain class of tri-atomic systems. Copyright © 2011 Wiley Periodicals, Inc.

International Journal of Quantum Chemistry

The adiabatic-to-diabatic transformation angle and the berry phase for coupled jahn-teller/renner-teller systems: The F + H 2 as a case study

Demonstration of onset of Jahn-Teller (JT) intersections, characterized by a topological phase of π, on introduction of bending in the collinear tetra-atomic C 2H 2 + cation, originally a Renner-Teller (RT) system, has raised interest in the study of the generality of this phenomenon. This interest has initiated similar study by shifting one external light atom from the collinear molecular axes of systems such as HCNH and HC 2O. Recent studies have revealed that slightly bent HCNH poses a specialty in this regard and thus demands focused attention. In the present work we performed a combined study using both the potential intersections and the angular nonadiabatic coupling terms (NACTs) and report two new results: (i) The first result is the appearance of the JT conical intersections (ci's) between the two lowest states of a slightly bent HCNH molecule (1 2A′ and 1 2A-3, originated from collinear X 2Π state) only with certain nonplanar configurations, in contrast to its appearance in C S configuration space (molecular plane) for slightly bent C 2H 2 +, HC 2O, or some other tetra-atomics. This is also associated with the first time demonstration of Berry phase for such a single isolated ci for HCNH molecule. (ii) For energetically higher potentials of slightly bent HCNH, the present study reveals the existence of the intersection of the state 1 2A-3 with the state 2 2A′ (originated from the collinear 1 2Σ + state); in contrast to the (1,2) ci this appears in the molecular plane. The search for ci's has been performed by varying the distances of the two H-atoms (designated as H C and H N) from the C-N axis as well as the dihedral angle φ between the two planes (H C,C,N) and (C,N,H N). Existence of these JT ci's results in deterioration of a two-state Hilbert subspace (HSS) model in diabatization, while the proper choice of an n (&gt;2)-state HSS circumvents this problem. © 2012 American Chemical Society.

Journal of Physical Chemistry A

Jahn-Teller intersections induced by introduction of bending in linear polyatomics: Study with HCNH, a selected molecular system

We present a study of the non-adiabatic coupling terms (NACTs) and the corresponding diabatic potentials for the reactive H2 + F system in the entrance channel. The study reveals two conical intersections (ci): (I) A Jahn-Teller (1, 2) ci, located at a point on the collinear HHF axis close to the minimum energy path; (II) A Renner-Teller line of (2, 3) cis, along the collinear HHF axis. To form the diabatic potentials we consider only the two lower adiabatic potentials and the quantized Born-Oppenheimer mixing angles that guarantee single-valued diabatic potentials. © 2011 Elsevier B.V. All rights reserved.

Chemical Physics Letters

Derivation of diabatic potentials for F + H2 employing non-adiabatic coupling terms

In this article are presented the first ever derived single-valued diabatic potentials for the reactive H 2 + F system based on a rigorous study of the conical intersection (ci) and Born-Oppenheimer non-adiabatic coupling terms (BO NACTs). This study revealed the existence of a Jahn-Teller (1, 2) ci located at a point on the collinear axis and a Renner-Teller (2, 3) ci along this axis. The diabatic potentials were calculated employing the rigorous adiabatic-to-diabatic transformation (ADT) angles (also known as mixing angles) which possess integer Berry phases along any closed contour at the region of interest in configuration space. The ADT angles were calculated employing BO NACTs and line integrals. © 2011 EDP Sciences, SIF, Springer-Verlag Berlin Heidelberg.

Journal	Chemical Physics
Publisher	-
ISSN	0301-0104
Open Access	No