Unimolecular
Fragmentation Induced By Low-Energy Collision:
Statistically or Dynamically Driven?
Martín-SómerAna
YáñezManuel
GaigeotMarie-Pierre
SpeziaRiccardo
2014
By
combining chemical dynamics simulations and RRKM statistical
theory we have characterized collision induced dissociation (CID)
mechanisms of [M(formamide)]<sup>2+</sup> ions (M = Ca, Sr) at different
timescales, from few femtoseconds to microseconds. Chemical dynamics
simulations account for the short-time and dynamically driven reactivity,
such as impulsive collision mechanism for formamide neutral loss.
From the simulations, we also got the amounts of energy transferred
during the collision and, especially important, the vibrational and
rotational energy distributions of the ions that did not react during
the simulation time length of 2.5 ps. These internal energy distributions
were in turn used in combination with RRKM theory to estimate the
rate constants of the possible reactive pathways. Hence, we performed
a statistical analysis of the CID dynamics accounting for the long-time
and statistical reactivity (i.e., through an IVR mechanism). This
multiscale approach allowed us to account for all the products observed
in the CID experimental spectra of [Ca(formamide)]<sup>2+</sup> and
[Sr(formamide)]<sup>2+</sup> doubly charged cations, as well as the
differences between them.