Infrared absorptions of NH3(H2) complexes trapped in solid neon

Area of Science:

• Physical Chemistry
• Spectroscopy
• Computational Chemistry

Background:

• Understanding molecular interactions is crucial in various chemical processes.
• Ammonia (NH3) is a fundamental molecule with significant industrial and biological relevance.
• The behavior of hydrogen (H2) in molecular complexes is of interest for energy and materials science.

Purpose of the Study:

• To investigate the formation and properties of hydrogen-ammonia (H2-NH3) molecular complexes.
• To characterize the vibrational spectra of H2 and NH3 within these complexes.
• To elucidate the structural and energetic aspects of H2-NH3 interactions.

Main Methods:

• Matrix isolation spectroscopy at cryogenic temperatures (4.3 K).
• Infrared absorption spectroscopy to detect vibrational modes.
• Ab initio and density functional theory (DFT) calculations for structural and spectral predictions.

Main Results:

• A new absorption at 4151.1 cm(-1) was observed, assigned to the H2 stretching fundamental in an H2-NH3 complex (H2 (j=1)).
• Additional absorptions near NH3 fundamentals confirmed the presence of NH3 moieties in H2-NH3 complexes (H2 (j=0) and H2 (j=1)).
• Experimental results were corroborated by computational predictions of the H2-NH3 structure with collinear H2 axis and NH3 threefold axis.

Conclusions:

• The study successfully identified and characterized H2-NH3 molecular complexes.
• Infrared spectroscopy revealed the activation of the H2 stretching vibration upon complexation with NH3.
• The findings indicate a propensity for forming complexes with multiple H2 molecules around NH3.