Nonvalence Correlation-Bound Anion States of Polycyclic Aromatic Hydrocarbons

Abstract

In this work, we characterize the nonvalence correlation-bound anion states of several polycyclic aromatic hydrocarbon (PAH) molecules. Unlike the analogous image potential states of graphene that localize the charge density of the excess electron above and below the plane of the sheet, we find that for PAHs, much of the charge distribution of the excess electron is localized around the periphery of the molecule. This is a consequence of the electrostatic interaction of the electron with the polar CH groups. By replacing the H atoms by F atoms or the CH groups by N atoms, the charge density of the excess electron shifts from the periphery to above and below the plane of the ring systems.

Ultrafast dynamics of low-energy electron attachment via a non-valence correlation-bound state

“…For example, several molecules such as C60and large polycyclic aromatic hydrocarbon anion have been calculated to support a CBS. 20,22,23,25 Here, we present compelling evidence for the formation of a non-valence CBS of C6F6followed by extremely efficient evolution of the CBS of into the valence-bound anion, preserving coherence into the vibrational modes of the valence-bound anion.…”

“…19 Indeed, calculations showed that correlation forces alone can be sufficient to bind an electron. [20][21][22][23][24][25] Hence, it has also been suggested that the presence of a non-valence CBS may facilitate electron attachment. 24 A most striking example of a non-valence CBS is in the anion of hexafluorobenzene, C6F6 -, where it is predicted to be bound by >100 meV.…”

Observation and ultrafast dynamics of a nonvalence correlation-bound state of an anion

“…However, many molecular systems do not have a sufficient dipole (or higher-order multipole) moment to support a dipole-bound state. Recently, high-level calculations on C 60 − ( 6 – 9 ), C 6 F 6 − ( 10 ), the coronene (C 24 H 12 ) anion ( 11 ), and certain nitrile-containing anion conformations ( 12 , 13 ) show that correlation forces between the excess electron and the valence electrons of the molecular system can give rise to a nonvalence correlation-bound state (CBS). In these examples, electrostatic interactions alone are insufficient to bind the excess electron.…”

“…Correlation forces tend to be larger in highly polarizable systems, and calculations have predicted nonvalence CBSs for a number of cluster systems: (NaCl) n − ( n = 3 and 4) ( 20 ), (C 6 F 6 ) 2 − ( 10 ), (C 24 H 12 ) 2 − ( 11 ), (Xe) n − ( n = 5 to 7) ( 21 ), (NH 3 ) 6 − ( 22 ), and (H 2 O) 24 − (and likely other water cluster anions) ( 23 , 24 ). There is a belief that correlation forces are a key ingredient in defining the structure of solvated electrons ( 25 ) and controlling electron mobility in liquid Xe ( 26 ).…”

Evidence of Electron Capture of an Outgoing Photoelectron Wave by a Nonvalence State in (C6F6)n–

“…[3][4][5] Beyond these electrostatic interactions, correlation forces can also bind electrons, leading to so-called non-valence correlation-bound states. [6][7][8][9][10][11][12][13] In reality, it is often a combination of these interactions that bind the electron in a very diffuse non-valence orbital. 2 The binding energy of such an orbital is typically very small, less than a few 100 meV.…”