Can Orbitals Really Be Observed in Scanning Tunneling Microscopy Experiments?

Helical orbitals and circular currents in linear carbon wires

“…possibility of experimental verication of the existence of helical orbitals spanning the length of linear molecules; a verication which ideally should be found by revisiting spectroscopic experiments on optical activity 11,[57][58][59] or with novel orbital imaging techniques. [60][61][62][63][64][65][66] Here, we will explore how the helical orbitals inuence the coherent electron transport properties of even [n]cumulenes with the aim of making explicit predictions for single-molecule conductance experiments.…”

Pleading for a Dual Molecular‐Orbital/Valence‐Bond Culture

“…Essays has been recently reaffirmed, [37] this is obviously not the case, since orbitals are neither unique nor observable,asmolecular energy and density are invariant to unitary orbital transformations within ag iven subspace,a sh as been recalled above.…”

“…This question has actually no answer, as it implies the fundamentally wrong assumption that orbitals would be some real, uniquely existing objects that could possibly be experimentally observed, just like, for example, electron densities, dipole moments, and so on. As has been recently reaffirmed, this is obviously not the case, since orbitals are neither unique nor observable, as molecular energy and density are invariant to unitary orbital transformations within a given subspace, as has been recalled above.…”

Orbitals and the Interpretation of Photoelectron Spectroscopy and (e,2e) Ionization Experiments

“…Although the obtained images resemble some textbook representations of occupied orbitals, several authors commented on these conclusions by stressing that, according to fundamental quantum mechanics, orbitals are not observable …”

“…[7,8] Although the obtained images resemble some textbook representations of occupied orbitals,s everal authors commented on these conclusions by stressing that, according to fundamental quantum mechanics,o rbitals are not observable. [9][10][11][12] Dauth et al [13] have explained that the correct interpretation of ARPES and EMS is that they provide Dyson orbitals,r ather than initial-state molecular orbitals,a nd that therefore these experiments have often been misinterpreted. This conclusion undermines claims that these experiments reflect "what actually electrons do in amolecule prior to their knock-out" [7] and therefore that hybrid molecular orbitals (HMOs) or localized molecular orbitals (LMOs) do not represent ap hysically valid orbital picture [7,8] In order to try to prevent these misinterpretations from gaining af oothold, we present some pedagogical background (see also previous articles along these lines [14,15] )t hat we hope will help clarify orbital concepts.T wo key points we emphasize are:1 )One cannot describe an N-electron wave function exactly in terms of N spin-orbitals,e ach containing one electron, and 2) a Dyson orbital is not an orbital of the molecule studied by photoelectron spectroscopy,and thus it is not an orbital in the usually understood sense,but rather it involves ageneralized use of the word "orbital" as an amplitude representation of the difference in the electron distribution of am olecule before and after ionization.…”