Zero kinetic energy spectroscopy of AlNH3 complex

Pulsed field ionization–zero kinetic energy photoelectron spectrum of the jet-cooled aluminum–ammonia complex, AlNH3, has been observed for the first time. The spectrum shows vibronic transitions from two spin–orbit levels of the neutral ground state, which allows the measurement of the following spectroscopic constants: ionization potential (39 746 cm−1), spin–orbit splitting (58 cm−1), intermolecular stretching vibrational frequencies (ω3+=339 cm−1, ω3+x3+=3.1 cm−1, and ν3=227 cm−1), and intermolecular bending frequency (ν6+=557 cm−1). The observation of the spin–orbit splitting confirms that the ground state of the neutral complex is the 2E state.