title: A joint theoretical and experimental study on diiodomethane: Ions and neutrals in the gas phase.
abstract: The chemical physics of halomethanes is an important and challenging topic in several areas of chemistry in particular in the chemistry of the atmosphere. Among the class of halomethanes, the diiodomethane molecule has attracted some interest in the last years, but despite this, the information on its radical cation [CH2I2](⋅+) is still limited. In this work, we measured and calculated the appearance energy (AE) of the ionic fragments I2(⋅+) and CH2(⋅+) and correlated the different fragmentation channels to the electronic states of the cation via photoelectron-photoion coincidence (PEPICO) experiments. In the case of the CH2/I2(⋅+) channel, the experimentally determined AE is in excellent agreement with the adiabatic theoretical value while a discrepancy is observed for the CH2(⋅+)/I2 channel. This discrepancy can be understood accounting for a fragmentation involving the formation of two I atoms (CH2(⋅+)/2I channel), which, as explained by time dependent density functional theory (TD-DFT) calculations, occurs when [CH2I2](⋅+) excited states are involved.
authors.affiliation: Dipartimento di Chimica, CNR-ISMN, Sapienza Università di Roma, Roma 00185, Italy.
authors.forename: Mauro
authors.initials: M
authors.lastname: Satta
authors.affiliation: CNR-ISM, Area della Ricerca di Roma 1, Monterotondo Scalo, RM 00015, Italy.
authors.forename: Paola
authors.initials: P
authors.lastname: Bolognesi
authors.affiliation: Dipartimento di Chimica, Sapienza Università di Roma, Roma 00185, Italy.
authors.forename: Antonella
authors.initials: A
authors.lastname: Cartoni
authors.affiliation: CNR-ISM, Area della Ricerca di Roma 1, Monterotondo Scalo, RM 00015, Italy.
authors.forename: Anna Rita
authors.initials: AR
authors.lastname: Casavola
authors.affiliation: CNR-ISM, Area della Ricerca di Roma 2, Roma 00133, Italy.
authors.forename: Daniele
authors.initials: D
authors.lastname: Catone
authors.affiliation: CNR-ISM, Area della Ricerca di Roma 1, Monterotondo Scalo, RM 00015, Italy.
authors.forename: Pal
authors.initials: P
authors.lastname: Markus
authors.affiliation: CNR-ISM, Area della Ricerca di Roma 1, Monterotondo Scalo, RM 00015, Italy.
authors.forename: Lorenzo
authors.initials: L
authors.lastname: Avaldi