Question

an electron is removed from the highest occupied molecular orbital in ​

Answer 1

Energy levels in molecules (highest occupied molecular orbital HOMO, lowest unoccupied molecular orbital LUMO, and states) and in condensed matter (VB, CB, and states) are important for applications such as in optics, electronic devices, catalysis, and electrochemistry. Weinhardt et al. demonstrate ex situ with a combination of ultraviolet photoemission spectroscopy (UPS) and inverse PES the determination of the electronic bandgap of tungsten oxide photoelectrodes.42 The samples were synthesized in Hawaii, packed under dry nitrogen and then shipped to Las Vegas for the ex situ spectroscopy measurements. They address the issue of sample aging in air and sample damage by irradiation by the XPS beam.