Photoelectron spectroscopy of HCCS radical.

Area of Science:

• Astrochemistry
• Molecular Physics
• Quantum Chemistry

Background:

• Linear carbon chains are prevalent in astrophysical environments.
• Sulfur-bearing carbon chains are important components of interstellar molecules.
• Understanding the properties of small molecules like HCCS is key to astrochemistry.

Purpose of the Study:

• To investigate the vacuum ultraviolet (VUV) photoionization of HCCS.
• To determine the adiabatic ionization energies of HCCS to its cation states.
• To provide experimental data for theoretical models of interstellar chemistry.

Main Methods:

• HCCS radical produced in situ from thiirane using a flow-tube reactor and microwave discharge.
• Vacuum ultraviolet (VUV) photoionization experiments.
• Ab initio calculations for vibronic structure assignment.

Main Results:

• Experimental measurement of adiabatic ionization energies for HCCS to the ground (X+Σ-3) and first excited (a+Δ1) cation states.
• Values obtained: 9.191 ± 0.003 eV (ground state) and 9.856 ± 0.003 eV (first excited state).
• Tentative ionization energy for the b+Σ+1 state measured at 10.364 ± 0.006 eV.

Conclusions:

• The study presents the first experimental ionization energies for HCCS.
• The data provides critical benchmarks for theoretical calculations and astrophysical models.
• This research contributes to the understanding of sulfur-containing molecules in space.