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Title:A diatomic molecule with extremely large amplitude motion in its vibrational states that have lengths of at least 12,000 angstroms.
Author(s):Dattani, Nikesh S.
Subject(s):Spectroscopy of Large Amplitude Motions
Abstract:The state-of-the-art empirical potential, \textit{and} the state-of-the-art \textit{ab initio} potential for the $b(1^3\Pi_{2_u})$ state of $^{7,7}$Li$_2$ agree with each other that the $(v=100,J=0)$ ro-vibrational state has an outer classical turning point larger than the diameter of most bacteria and many animal cells. The 2015 empirical potential\footnote{Dattani (2015)} based on a significant amount of spectroscopic data, predicts the $(v=100,J=0)$ level to be bound by only 0.000$\,$000$\,$000$\,$004$\,$cm$^{-1}$ (\textless\, 0.2 Hz). The outer turning point of the vibrational wavefunction is about 671\,000$\,$\AA \,or 0.07$\,$mm. Here, the two Li atoms are bound to each other, despite being nearly as far apart as the lines on a macroscopic ruler. The 2014 \textit{ab initio} calculation based on a powerful Fock space MRCC method\footnote{Musial \& Kucharski (2014) Journal of Chemical Theory and Computation, \textbf{10}, 1200.} and with the long-range tail anchored by $C_3^{^7\rm{Li}}/r^3$ with the ultra-high precision 2015 value of $C_3^{^7\rm{Li}}$, has this same level bound by 0.000$\,$000$\,$000$\,1\,$cm$^{-1}$ (\textless\, 3 Hz), with an outer turning point of $>0.01\,$mm. While this discovery occurred during a study of Li$_2$, the $b(1^3\Pi_{2_u})$ states of heavier alkali diatomics are expected to have even larger amplitude vibrational states. While it might be tempting to call these very large molecules ``Rydberg molecules", it is important to remember that this term is already used to describe highly excited \textit{electronic} states whose energy levels follow a formula similar to that for the famous Rydberg series. The highly delocalized \textit{vibrational} states are a truly unfamiliar phenomenon.
Issue Date:2016-06-20
Publisher:International Symposium on Molecular Spectroscopy
Genre:Conference Paper/Presentation
Rights Information:Copyright 2016 by the authors
Date Available in IDEALS:2017-01-26

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