Photodissociation of aniline N–H bond in clusters of different nature

0446951 - ÚFCH JH 2016 RIV GB eng J - Journal Article
Poterya, Viktoriya - Nachtigallová, Dana - Lengyel, Jozef - Fárník, Michal
Photodissociation of aniline N–H bond in clusters of different nature.
Physical Chemistry Chemical Physics. Roč. 17, č. 38 (2015), s. 25004-25013. ISSN 1463-9076. E-ISSN 1463-9084
R&D Projects: GA ČR GA14-14082S
Institutional support: RVO:61388955 ; RVO:61388963
Keywords : NONADIABATIC COUPLING TERMS * MR-CI LEVEL * PHOTOEXCITED ANILINE
Subject RIV: CF - Physical ; Theoretical Chemistry
Impact factor: 4.449, year: 2015

We investigated the solvent effects on the N–H bond photodisociation dynamics of aniline (PhNH2) in clusters using velocity map imaging (VMI). The VMI experiment was accompanied by a time-of-flight mass spectrometry after electron ionization to reveal the cluster nature. The H-fragment images were recorded at 243 nm in various expansion regimes corresponding to different species: isolated molecules; small (PhNH2)N, N ≤ 3, clusters; larger (PhNH2)N, N ≥ 10; small mixed PhNH2·(H2O)N, N ≤ 10, clusters; and individual PhNH2 molecules deposited on large (H2O)N, ¯N = 430. The H-fragment kinetic energy distributions exhibit fast fragments around 0.8 eV (A) assigned previously to a direct dissociation along a repulsive ps * state potential, and slow statistical fragments peaking near 0.2 eV (B). In the aniline clusters the contribution of fast fragments (A) decreases relative to (B) with increasing the cluster size. Similar effect is observed when aniline is solvated with water molecules. The experimental data are interpreted with ab initio calculations. Cluster structures were calculated with both N–H bonds of an aniline molecule participating in hydrogen bonding, as well as the ones with free N–H bonds. The latter ones yield preferentially the fast fragments as the isolated molecule. For the N–H engaged in hydrogen bonding a barrier increased along the N–H coordinate on the dissociative ps * state potential surface, and also the energy of ps */S0 conical intersection increased. Thus the fast dissociation channel was closed stabilizing the molecule in clusters. The population could be funnelled through other conical intersections into the hot ground state which decayed statistically, yielding the slow H-fragments.
Permanent Link: http://hdl.handle.net/11104/0248938