Combined gas electron diffraction and mass spectrometric experimental setup at Bielefeld University

Area of Science:

• Physical Chemistry
• Molecular Spectroscopy
• Materials Science

Background:

• Gas electron diffraction is a powerful technique for determining molecular structures.
• Synchronous measurements of mass spectra can provide complementary information.
• Acetic acid is a model system for studying hydrogen bonding in the gas phase.

Purpose of the Study:

• To design and validate a combined experimental setup for simultaneous electron diffraction and mass spectrometry.
• To refine the molecular structures and mole fractions of acetic acid monomer and dimer.
• To demonstrate the utility of mass spectrometry in gas electron diffraction experiments.

Main Methods:

• Development of a combined experimental setup for synchronous electron diffraction and mass spectrometry.
• Gas-phase experiments on acetic acid at 296 K and 457 K.
• Analysis of electron diffraction intensities incorporating mass spectral data.

Main Results:

• Successfully refined molecular structures and mole fractions of acetic acid monomer and dimer.
• Demonstrated the capability to detect sample decomposition, aiding experimental optimization and data interpretation.
• Determined the hydrogen bond length in the acetic acid dimer (r _e (O ⋯ H) = 1.657(9) Å ), consistent with theoretical predictions.

Conclusions:

• The combined electron diffraction and mass spectrometry approach is crucial for accurate gas-phase structural analysis.
• Mass spectrometry is vital for monitoring sample integrity and optimizing experimental conditions.
• Acetic acid diffraction patterns are recommended for calibrating pressure in diffraction volumes.