Studies of intersystem crossing dynamics in acetylene

Area of Science:

• Theoretical Chemistry
• Spectroscopy
• Computational Physics

Background:

• Acetylene's T3 potential energy surface is crucial for understanding its excited electronic states.
• Previous spectroscopic studies revealed local perturbations in the S1 3nu3 state.
• The origin of these perturbations required further theoretical investigation.

Purpose of the Study:

• To perform a new ab initio study of the acetylene T3 potential energy surface.
• To clarify the nature of the energy minimum and compute key molecular properties.
• To interpret observed spectroscopic perturbations in the S1 3nu3 state.

Main Methods:

• Ab initio electronic structure calculations.
• Computation of equilibrium geometries and diabatic frequencies.
• Calculation of harmonic vibrational overlap integrals.

Main Results:

• The study clarifies the energy minimum of the acetylene T3 potential energy surface.
• Computed data enabled the calculation of vibrational overlap integrals.
• Results support the assignment of spectral perturbations to a single T3 vibrational state.

Conclusions:

• The computed results provide a theoretical basis for interpreting experimental spectroscopic data.
• The findings resolve ambiguities regarding the origin of perturbations in the S1 3nu3 state.
• Plausible assignments are proposed to guide future experimental investigations.