Coauthored Publications with: Muthiah

Conference Paper

Kasai, T, Muthiah B, Lin K-C.  2017.  Role of cooperative network interaction in transition region of roaming reactions: Non-equilibrium steady state vs. thermal equilibrium reaction scheme. AIP Conference Proceedings. 1906 Abstract

This paper proposes a new type of roaming mechanism. We find a signature of trajectory with chaotic behavior in the action-angle diagram of the H + H2 reaction on a LEP surface, namely the trajectory is found to be very sensitive to the initial angle variable which corresponds to the phase of the H2 vibration. The trajectory pattern switches from the direct to the complex forming mechanism, and vice versa, in the angle range (0 ∼ π). In the complex forming angle range, trajectories switch from reactive to non-reactive randomly and suddenly, as the result, we cannot predict the collision pattern from the initial conditions. Therefore, we may classify such trajectory as a new type of roaming with chaotic behavior, and it is different from the ordinary trajectory with deterministic behavior. This chaotic behavior could be due cooperative nearby network interaction (CNN effect). We also suggest that the KPP (Kolmogorow-Petrovsky-Piskounov) equation is useful to estimate the density gradient of the activated reagents, so that one can evaluate the branching ratio to various exit channels, such as triple fragmentation, tight transition state, or the roaming channel with the aid of the present classical trajectory calculation. © 2017 Author(s).

Journal Article

Kasai, T, Che D-C, Tsai P-Y, Nakamura M, Muthiah B, Lin K-C.  2018.  Roaming and chaotic behaviors in collisional and photo-initiated molecular-beam reactions: a role of classical vs. quantum nonadiabatic dynamics. Rendiconti Lincei. 29:219-232., Number 2 AbstractWebsite

A new reaction scheme is proposed to account for roaming and chaotic behaviors in collisional and photo-initiated molecular-beam reactions, where nonadiabatic dynamics plays a key role and the collapse of superposition of wave functions is considered to be important in the beginning of the present scheme. Since the feature of molecular orbitals of reagents is crucial in reaction, we showed how to map out the spatial distribution of the relevant HOMO molecular orbitals of CH3Cl in the impact of fast electrons. We identified by experiment that the multiple overlap of nearby molecular orbitals affects even the vibrational motion of adjacent molecule DCl of the transient [ClDCl] chemical species. We also showed dynamical steric effects in the HBr + OH four-atom reaction as a manifestation of the nonadiabatic dynamics in complex systems. The roaming mechanism in the photo-initiated reaction of methyl formate is clarified in detail by experiment as well as the QCT trajectory calculation, where the conical intersection region plays an essential role. We suggest that two types of roaming trajectories coexist, i.e., deterministic and chaotic roaming trajectories based on classical trajectory calculations. To clarify the nonadiabatic dynamics in the roaming mechanism for non-collinear three-dimensional (3D) collisions, a new model of the 3D Polanyi rule is proposed as the extension of the well-established 2D Polanyi rule. In the 3D Polanyi rule, it is expected that the curvature and torsion of Frenet–Serret formulas in three-dimensional space would provide us key concepts in understanding reaction dynamics. © 2018, Accademia Nazionale dei Lincei.
Muthiah, B, Paredes-Roibás D, Kasai T, Lin K-C.  2019.  Photodissociation of CH2BrI using cavity ring-down spectroscopy: in search of a BrI elimination channel. Physical Chemistry Chemical Physics. 21(26):13943-13949. AbstractWebsite

Photodissociation of CH2BrI was investigated in search of unimolecular elimination of BrI via a primary channel using cavity ring-down absorption spectroscopy (CRDS) at 248 nm. The BrI spectra were acquired involving the first three ground vibrational levels corresponding to A3Π1 ← X1Σ+ transition. With the aid of spectral simulation, the BrI rotational lines were assigned. The nascent vibrational populations for v′′ = 0, 1, and 2 levels are obtained with a population ratio of 1:(0.58 ± 0.10):(0.34 ± 0.05), corresponding to a Boltzmann-like vibrational temperature of 713 ± 49 K. The quantum yield of the ground state BrI elimination reaction is determined to be 0.044 ± 0.014. The CCSD(T)//B3LYP/MIDI! method was employed to explore the potential energy surface for the unimolecular elimination of BrI from CH2BrI.