The Multiphoton Ionization Spectrum of Methyl Iodide Revisited: 1.67-2.2 ev Excitation

Abstract

Abstract. The study of the multiphoton ionization of methyl iodide has a long and storied history. Here, we revisit this topic and present spectra of each of the photoionization and photodissociation fragments (C + , CH + , CH + 2 , CH + 3 , CH 3 I + , and I + ) using a custom time-offlight mass spectrometer and a tunable dye laser over the excitation range of 550-740 nm (2.2-1.67 eV). The choice of this wavelength range allows for excitation through the A state and resonant ionization through higher energy levels using 4+1, 5+1, or 6+1 photons for excitation and ionization. Although the various fragments yield very similar spectra, fewer fragment ions are observed with increasing wavelength.