Journal of Physical Chemistry A, Vol.101, No.4, 685-689, 1997
Dissociation of State-Selected No2+ Ions Studied by Threshold Photoelectron-Photoion Coincidence Techniques
Fragmentation patterns and dissociation rates of state-selected NO2+ ions were measured by the threshold photoelectron-photoion coincidence (TPEPICO) method in the region of 40-100 nm. Parent NO2+ ions were detected when they were prepared in the excited states located above the first dissociation limit (D-0(0) = 2.79 eV), correlating to NO+(X(1) Sigma(+)) + O(P-3). Specially, the dissociation rate (k(dis)) of NO2+ ions in the lowest excited <(a)over tilde B-3(2)> State increases with increasing the quantum number of the bending vibration (n(2)) : (7.4 +/- 4.9) x 10(2), (1.32 +/- 0.56) x 10(3), (1.51 +/- 0.40) x 10(4), and (2.38 +/- 0.51) x 10(4) s(-1) for n(2) = 0, 1, 2, and 3, respectively. The branching ratios of two dissociation pathways, NO+ + O and O+ + NO, were found to depend on the electronic state of the parent ion. The unimolecular dissociation channels are discussed in terms of dissociation potential surfaces open for individual electronic states and radiative relaxation to lower electronic states.
Keywords:157 NM PHOTODISSOCIATION;EXCITATION SPECTRUM;MOLECULE REACTIONS;TESICO TECHNIQUE;CO2;APPARATUS