When using a given basis set, both energy and this quantity are multiplied by a dimensionless scaling factor usually close to 1 to account for a term called ZPVE. For a transition state, this quantity takes on an imaginary (15[1])value (-5[1])since it corresponds to a negative eigenvalue of the mass-weighted (15[1])Hessian (15[1])of a (-5[1])Born-Oppenheimer surface. Olfactory receptors identify molecules by their value for this quantity, according to the controversial ■END■