Probing the ionization potentials of the formaldehyde dimer.

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Spectroscopy

Background:

• Formaldehyde dimer (H2CO)2 is a key molecule in atmospheric and interstellar chemistry.
• Understanding its electronic properties, such as ionization potentials (IPs), is crucial for interpreting experimental data.

Purpose of the Study:

• To computationally investigate the ionization potentials (IPs) of the formaldehyde dimer.
• To provide high-level theoretical predictions to guide experimental photoionization studies.

Main Methods:

• Employed high-level coupled cluster theory, including equation-of-motion ionization potential coupled-cluster with single and double (EOMIP-CCSD) excitations.
• Utilized large correlation-consistent basis sets with extrapolation to the complete basis set limit.
• Calculated IPs for both C2h and Cs conformers of the formaldehyde dimer.

Main Results:

• Computed twelve lowest-lying IPs for both C2h and Cs formaldehyde dimer conformers.
• Achieved excellent agreement between different high-level computational approaches.
• Obtained excellent agreement for formaldehyde monomer IPs compared to experimental data.
• Calculated binding energy of -4.71 kcal/mol for the C2h dimer and isomerization energy of 0.76 kcal/mol.

Conclusions:

• This work presents the first high-level theoretical determination of IPs for formaldehyde dimer conformers.
• The findings provide valuable data for experimental photoionization investigations.
• The calculated binding and isomerization energies offer insights into dimer stability.