Effect of Microsolvation on Nonstatistical Behavior of HO3•$\text{HO}_{3}^{\cdot}$

Hydrotrioxyl radical ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:semantics> <mml:mrow><mml:msubsup><mml:mtext>HO</mml:mtext> <mml:mrow><mml:mn>3</mml:mn></mml:mrow> <mml:mrow><mml:mo>•</mml:mo></mml:mrow> </mml:msubsup> </mml:mrow> <mml:annotation>$\text{HO}_{3}^{\cdot}$</mml:annotation></mml:semantics> </mml:math> ) is proposed as a transient species in various important atmospheric reactions. One factor that can influence the lifetime of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:semantics> <mml:mrow><mml:msubsup><mml:mtext>HO</mml:mtext> <mml:mrow><mml:mn>3</mml:mn></mml:mrow> <mml:mrow><mml:mo>•</mml:mo></mml:mrow> </mml:msubsup> </mml:mrow> <mml:annotation>$\text{HO}_{3}^{\cdot}$</mml:annotation></mml:semantics> </mml:math> in the atmosphere is its ability to form complexes with water monomers and dimers, i.e., microsolvated systems. In addition, a recent study suggests that the lifetime of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:semantics> <mml:mrow><mml:msubsup><mml:mtext>HO</mml:mtext> <mml:mrow><mml:mn>3</mml:mn></mml:mrow> <mml:mrow><mml:mo>•</mml:mo></mml:mrow> </mml:msubsup> </mml:mrow> <mml:annotation>$\text{HO}_{3}^{\cdot}$</mml:annotation></mml:semantics> </mml:math> is greatly influenced by the non-Rice-Ramsperger-Kassel-Marcus (RRKM) effect, and hence, the role of water complexation in determining the lifetime of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:semantics> <mml:mrow><mml:msubsup><mml:mtext>HO</mml:mtext> <mml:mrow><mml:mn>3</mml:mn></mml:mrow> <mml:mrow><mml:mo>•</mml:mo></mml:mrow> </mml:msubsup> </mml:mrow> <mml:annotation>$\text{HO}_{3}^{\cdot}$</mml:annotation></mml:semantics> </mml:math> is incomplete without estimating the nonstatistical effect in HO₃··(H₂O)_n (n = 1 and 2) complexes. Therefore, in the present work, using direct dynamics simulations along with high-level electronic structure theory, the stability of these microsolvated systems is studied. The investigation suggests that the microsolvation of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:semantics> <mml:mrow><mml:msubsup><mml:mtext>HO</mml:mtext> <mml:mrow><mml:mn>3</mml:mn></mml:mrow> <mml:mrow><mml:mo>•</mml:mo></mml:mrow> </mml:msubsup> </mml:mrow> <mml:annotation>$\text{HO}_{3}^{\cdot}$</mml:annotation></mml:semantics> </mml:math> reduces its lifetime, and the non-RRKM effect is negligible as the system approaches the solution-phase.