Aqueous Ammonium Nitrate Investigated Using Photoelectron Spectroscopy of Cylindrical and Flat Liquid Jets

Area of Science:

• Physical Chemistry
• Surface Science
• Spectroscopy

Background:

• Ammonium nitrate solutions are crucial in various industrial and environmental processes.
• Understanding the surface behavior of ions in aqueous solutions is vital for chemical and physical processes.
• Synchrotron radiation-based photoelectron spectroscopy offers a powerful tool for probing electronic structures of liquids.

Purpose of the Study:

• To investigate the electronic properties and surface distribution of ammonium (NH4+) and nitrate (NO3-) ions in aqueous solutions.
• To determine the photoionization anisotropy (β parameter) of N 1s electrons from NH4+ and NO3-.
• To explore the photon energy dependence of photoelectron signals and surface distribution of these ions.

Main Methods:

• Utilized synchrotron radiation-based photoelectron spectroscopy with cylindrical microjet and flat jet nozzles.
• Measured electron emission at 90° and magic angle (54.7°) relative to polarization.
• Employed SESSA simulations for background normalization and analyzed β parameter as a function of photon energy (470-530 eV).

Main Results:

• Obtained β parameter values for N 1s ionization of NH4+ and NO3-, with NH4+ showing a higher value by ≈0.1.
• Observed photon energy-dependent cross-section variation for NO3- signal, but not for NH4+.
• Found that the NH4+ to NO3- peak area ratio remained constant with takeoff angle, irrespective of nozzle type.

Conclusions:

• The study provides insights into the distinct photoionization dynamics of NH4+ and NO3- ions in aqueous solution.
• Results suggest a similar distribution of ammonium and nitrate ions in the surface region of the solution.
• The findings contribute to a better understanding of ionic behavior at liquid surfaces using advanced spectroscopic techniques.