In the Photoelectron Spectrum of Carbon Disulfide, CS₂, Ionization from the Highest

Multiple Choice

In the photoelectron spectrum of carbon disulfide, CS₂, ionization from the highest occupied, 1_g, molecular orbital results in little vibrational structure. In contrast, ionization from the next lowest occupied 1_u molecular orbital results in a long vibrational progression in the ₁ symmetric stretching mode of the CS₂⁺ ion. Which of the following descriptions of the bonding in neutral CS₂ best explains these observations?

A) Both the 1_g and 1_u molecular orbitals of CS₂ are non-bonding in character.
B) The 1_g molecular orbital of CS₂ is antibonding in character and the 1_u orbital is non-bonding in character.
C) The 1_g molecular orbital of CS₂ is nonbonding in character and the 1_u orbital is bonding in character.
D) Both the 1_g and 1_u molecular orbitals of CS₂ are antibonding in character.