Electron collisions with the ${\text{CH}}_2{\text{O-H}}_2\text{O}$ complex

We report cross sections for elastic collisions of low-energy electrons with the ${\text{CH}}_2{\text{O-H}}_2\text{O}$ complex. We employed the Schwinger multichannel method with pseudopotentials in the static-exchange and in the static-exchange-polarization approximations for energies from 0.1 to 20 eV. We considered four different hydrogen-bonded structures for the complex that were generated by classical Monte Carlo simulations. Our aim is to investigate the effect of the water molecule on the ${\pi }^{\ast }$ shape resonance of formaldehyde. Previous studies reported a ${\pi }^{\ast }$ shape resonance for ${\text{CH}}_2\text{O}$ at around 1 eV. The resonance positions of the complexes appear at lower energies in all cases due to the mutual polarization between the two molecules. This indicates that the presence of water may favor dissociation by electron impact and may lead to an important effect on strand breaking in wet DNA by electron impact.

Figure 1

(Color online) Geometrical structures of formaldehyde, water, and the four possible structures of the complexes (hydrogen-bonded pairs ${\text{CH}}_2{\text{O-H}}_2\text{O}$) named $A$, $B$, $C$, and $D$. These plots were generated using MACMOLPLT [15].

Figure 2

(Color online) Momentum transfer cross sections for ${\text{H}}_2\text{O}$ (left upper panel) and ${\text{CH}}_2\text{O}$ (right upper panel) and for the four complexes (lower panels) in the SE and SEP approximations.

Figure 3

(Color online) LUMOs for formaldehyde and the complexes $A$, $B$, $C$, and $D$. See text for discussion. These plots were generated using MACMOLPLT [15].