Photofragmentation spectroscopy of cold protonated aromatic amines in the gas phase

Géraldine Féraud (1) , Michel Broquier (2, 3) , Claude Dedonder (1) , Gilles Grégoire (4) , Satchin Soorquia (2) , Christophe Jouvet (1)

1 PIIM - Physique des interactions ioniques et moléculaires
2 ISMO - Institut des Sciences Moléculaires d'Orsay
3 CLUPS - Centre Laser de l'Université Paris Sud
4 LPL - Laboratoire de Physique des Lasers

The electronic spectroscopy of cold protonated aromatic amines, anilineH+ C6H5-NH3+, benzylamineH+ C6H5-CH2-NH3+ and phenethylamineH+ C6H5-(CH2)2-NH3+ has been investigated experimentally in a large spectral domain and is compared to that of their hydroxy- homologues (OH containing). In the low energy region, the electronic spectra are similar to their neutral analogues, which reveals that their first excited state is of * character. A second transition is observed from 0.5 to 1 eV above the origin band, which is assigned to the excitation of the * state. In these protonated amine molecules, there is a competition between different fragmentation channels, some of them being specific of the UV excitation and are not observed in low-energy collision induced dissociation experiment. Besides, a drastic change in the fragmentation branching ratio can be observed within a very short energy range that reveals the complex excited state dynamics and fragmentation processes in these species. The experimental observations can be rationalized with a simple qualitative model, the /* model(PCCP-2002), which predicts that the excited state dynamics is controlled by the crossing between the * excited state and a  state repulsive along the XH (X being O or N) coordinate.

Mots clés: protonated molecule ion spectroscopy

Domaines: Agrégats Moléculaires et Atomiques [physics.atm-clus]

Géraldine Féraud, Michel Broquier, Claude Dedonder, Gilles Grégoire, Satchin Soorquia, et al.. Photofragmentation spectroscopy of cold protonated aromatic amines in the gas phase. Physical Chemistry Chemical Physics, 2014, ⟨10.1039/C3CP54736A⟩. ⟨hal-00920405⟩