Sulfur Molecules in Space by X-rays: A Computational Study

Area of Science:

• * Astrochemistry
• * Computational astrophysics
• * Spectroscopy

Background:

• * X-ray astronomy requires high-resolution spectra of interstellar molecules and dust for accurate interstellar medium studies.
• * Theoretical models must be validated against experimental data before application in upcoming X-ray missions.
• * Sulfur-containing molecules are vital in astrochemistry, but their X-ray spectral data is often lacking.

Purpose of the Study:

• * To calculate and predict sulfur K-edge X-ray absorption spectra for interstellar molecules H₂S, SO₂, OCS, and CS.
• * To assess the reliability of various computational methods, including algebraic-diagrammatic construction (ADC) and coupled cluster (CC) approaches, against experimental data.
• * To aid in the detection and analysis of sulfur-bearing molecules in space using X-ray telescopes.

Main Methods:

• * Calculation of sulfur K-edge X-ray absorption spectra using core-valence separation (CVS) with ADC(2)-x and CC3 methods.
• * Application of transition potential density functional theory (TP-DFT) for comparison.
• * Validation of computational results against existing experimental spectra for H₂S, SO₂, and OCS.

Main Results:

• * CVS-ADC(2)-x and CVS-CC3 methods provide good qualitative agreement with experimental spectra for H₂S, SO₂, and OCS.
• * The TP-DFT method demonstrated unreliability for modeling the X-ray spectra of these molecules.
• * Predicted X-ray spectrum for CS, a molecule not yet measured experimentally.

Conclusions:

• * CVS-based computational methods show promise for interpreting experimental X-ray spectra of interstellar molecules.
• * Further advancements are needed for quantitative agreement between theoretical calculations and experimental data.
• * Reliable spectral data is essential for advancing interstellar medium research with future X-ray missions.