Electron impact ionisation and UV absorption study of α- and β-pinene

We have performed a coordinated set of experiments to measure the electron impact ionisation and UV photoabsorption cross sections of α- and β-pinene. The adiabatic ionisation energies of α- and β-pinene were derived from experiment and found to be 8.3 and 8.6 eV which compared well with high-level quantum chemical calculations (G3MP2) yielding values of 8.29 and 8.41 eV. Additionally, vertical ionisation energies of 8.62 and 8.96 eV were calculated using an OVGF method. UV photoabsorption cross sections were measured using a high-resolution synchrotron radiation source and electronic states interpreted on the basis of the TD quantum chemical methods.