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

Ammonium nitrate in aqueous solution was investigated with synchrotron radiation based photoelectron spectroscopy using two types of liquid jet nozzles. Electron emission from a cylindrical microjet of aqueous ammonium nitrate solution was measured at two different angles relative to the horizontal polarization of the incident synchrotron radiation, 90° and 54.7° (the "magic angle"), for a range of photon energies (470-530 eV). We obtained β parameter values as a function of photon energy, based on a normalization procedure relying on simulations of background intensity with the SESSA (Simulation of Electron Spectra for Surface Analysis) package. The β values are similar to literature data for O 1s ionization of liquid water, and the β value of N 1s from NH 4 + is higher than that for NO 3 - , by ≈0.1. The measurements also show that the photoelectron signal from NO 3 - exhibits a photon energy dependent cross section variation not observed in NH 4 + . Additional measurements using a flat jet nozzle found that the ammonium and nitrate peak area ratio was unaffected by changes in the takeoff angle, indicating a similar distribution of both ammonium and nitrate in the surface region.