Quantum Scattering Study of NCCNH⁺-H₂ Collision Under Interstellar Conditions

Area of Science:

• Chemical Physics
• Quantum Chemistry
• Astrophysics

Background:

• Protonated cyanogen (NCCNH+) is a newly detected interstellar molecule.
• Understanding its rotational dynamics is key for interpreting astronomical observations.
• Cold collisions with hydrogen (H2) are fundamental for determining molecular populations in space.

Purpose of the Study:

• To calculate state-to-state rate coefficients for rotational transitions of NCCNH+.
• To investigate the influence of para- and ortho-hydrogen on these dynamics.
• To provide data essential for astrophysical modeling of NCCNH+.

Main Methods:

• Ab initio calculation of the 4D potential energy surface (PES) using CCSD(T)-F12b.
• Fitting the PES using a neural network (NN) model for enhanced accuracy.
• Expansion of the PES using bispherical harmonics and analytic function representation.
• Close-coupling calculations for cross-sections and rate coefficients up to j=16.

Main Results:

• State-to-state rate coefficients for NCCNH+ rotational transitions were computed.
• Calculations considered collisions with both para- and ortho-hydrogen.
• The computed rates exhibit behavior similar to NCCN-H2 collisions, but with lower magnitudes.

Conclusions:

• The study provides essential collisional data for NCCNH+.
• This data aids in the interpretation of astronomical observations of this molecule.
• The methodology establishes a framework for studying similar molecular systems.