Study of nonadibatic effect on dissociation channels of HCNH – the
issue of abundance ratio [HNC]/[HCN] in upper atmosphere
revisited.
Abstract
The abundance ratio [HNC]/[HCN] in upper atmosphere is known to
vary depending on the various conditions, like the presence of UV
radiation, the temperature of the region of abundance, etc. There have
been attempts to justify the related observations from kinetic as well
as thermodynamic considerations. In the present work we consider the
dissociation of HCNH, right after its formation from electron capture of
HCNH+, as the primary source of HNC and HCN in upper atmosphere. Few
years back, from our group, a study [J.Phys.Chem.A, 2013, 117,
8680-8690] of nonadiabatic effect on low-lying excited states of HCNH
was undertaken to understand the formation of HNC. Present study is to
explore the nonadiabatic effects on the various dissociation channels of
HCNH leading to the formation of HCN and thus to justify the abundance
ratio [HNC]/[HCN] in upper atmosphere. We present here the first
ever exploration of the presence of conical intersection around the
transition state geometries along the intrinsic reaction coordinate for
the dissociation of HCNH into HCN and HNC.