Photodissociation and photoionization of pyrrole following the multiphoton excitation at 243 and 364.7 nm

Abstract

Photoelectron imaging and time of flight mass spectrometry are used to study the multiphoton ionization and dissociation of pyrrole and its cation following excitation at 243 nm and at 364.7 nm. Our results confirm the 8.2 eV ionization potential of pyrrole and the 9.2 eV ionization threshold for forming the 2B1 first excited state of the cation. Prompt photolysis of the N-H bond in neutral pyrrole following one-photon excitation to its 1 1A2 neutral excited state is inferred from analysis of the two-photon photoelectron spectrum recorded at 243 nm, confirming the findings of recent translational spectroscopy studies. Facile dissociation of the pyrrole cation is also observed following excitation at 243 nm; analysis of the fragment cations indicates the operation of a complex dissociation mechanism involving dual bond fission and possible migration of the H atom originally bonded to the nitrogen heteroatom.

Mass spectrometry of hydrogen bonded clusters of heterocyclic molecules: Electron ionization vs. photoionization

“…Therefore we refer to the NIST database spectra [29] for comparison. The proposed assignment of the mass peaks in our UVMPI TOF mass spectra is based on comparison to the photoionization spectra in the literature [5][6][7], where also the discussion of this assignment can be found, which is, however, not the point here.…”

“…Ionization of the gas phase pyrrole [5,6] and imidazole [7], as well as the imidazole in water environment [8] was studied previously. Ionization of the clusters of these molecules was explored to a much lesser extent [9].…”

Non-adiabatic dynamics of pyrrole: Dependence of deactivation mechanisms on the excitation energy

“…Photofragment spectroscopy has revealed the presence of the large fragments HCN, C 3 H 4 , C 3 H 3 , and CNH 2 in different fractions depending on the pump wavelength [4,5,26,27] The appearance of such fragments also seems to imply the existence of other internal conversion mechanisms occurring in competition with the NH-stretching. It has been proposed that such mechanisms would involve ring puckering [28] and ring opening [23,29] processes ( Fig.…”

Development of Multiphoton Ionization Technique for Detection of Polycyclic Aromatic Hydrocarbon (PAH) in Solution

“…The ionization threshold for all PHAs is about 9 eV (c.a. 138 nm) [9]. This light source is impossible to generate at ambiance condition because of the strong absorbance of oxygen in the air.…”

“…The photocurrent waveform describes several dynamic processes such as the motion of ions and electrons in liquid medium, the quenching of ion flow by the other molecules (solute, residual impurities etc. ), recombination of anions and cations or charge transfer between ions and the molecules [9] [10].…”