Imaging superatomic molecular orbitals in a C60 molecule through four 800-nm photons

Abstract

Superatomic molecular orbitals (SAMOs) in C 60 are ideal building blocks for functional nanostructures. However, imaging them spatially in the gas phase has been unsuccessful. It is found experimentally that if C 60 is excited by an 800-nm laser, the photoelectron casts an anisotropic velocity image, but the image becomes isotropic if excited at a 400-nm wavelength. This diffuse image difference has been attributed to electron thermal ionization, but more recent experiments (800 nm) reveal a clear nondiffuse image superimposed on the diffuse image, whose origin remains a mystery. Here we show that the nondiffuse anisotropic image is the precursor of the f SAMOs. We predict that four 800-nm photons can directly access the 1f SAMO, and with one more photon, can image the orbital, with the photoelectron angular distribution having two maxima at 0° and 180° and two humps separated by 56.5°. Since two 400-nm photons only resonantly excite the spherical 1s SAMO and four 800-nm photons excite the anisotropic 1f SAMO, our finding gives a natural explanation of the nondiffuse image difference, complementing the thermal scenario.