The failure of CS approximation in quantum reaction scattering with double deep well: Time-dependent calculation for O + NH reaction

Abstract

The present paper shows the failure of CS (centrifugal sudden or coupled states) approximation in the time-dependent (TD) quantum wave packet calculation for the exoergicity reaction O + NH on the 1A′ potential energy surface [Guadagnini, Schatz and Walch, J Chem Phys 102:774 (1995)] that has double deep wells. In order to show this, total reaction probabilities and rate constants for the title reaction are presented in this study with the CS approximation and the CC (close-coupling) method, respectively. The results show that by carrying out the wave packet propagation to several picoseconds with the CC method, we can resolve all the resonance features for the title reaction and the differences between the CS and the CC become larger as J becomes larger. When J becomes larger the agreement between the CS and the CC gets progressively worse. The failure of the CS approximation can be explained with the results of double deep wells, which cause long propagation time and make the coupling of K states important. © World Scientific Publishing Company.