Related Experiment Video
Updated: Jan 3, 2026

Infrared Degenerate Four-wave Mixing with Upconversion Detection for Quantitative Gas Sensing
Published on: March 22, 2019
Revisiting the photoabsorption spectrum of NH3 in the 5.4-10.8 eV energy region
P Limão-Vieira1, N C Jones2, S V Hoffmann2
1Atomic and Molecular Collisions Laboratory, CEFITEC, Department of Physics, Universidade NOVA de Lisboa, 2829-516 Caparica, Portugal.
Abstract:
We present a comprehensive revisited experimental high-resolution vacuum ultraviolet (VUV) photoabsorption spectrum of ammonia, NH3, covering for the first time the full 5.4-10.8 eV energy-range, with absolute cross sections determined. The calculations on the vertical excitation energies and oscillator strengths were performed using the equation-of-motion coupled cluster method restricted to single and double excitation levels and used to help reanalyze the observed Rydberg structures in the photoabsorption spectrum. The VUV spectrum reveals several new features that are not previously reported in the literature, with particular reference to the vibrational progressions of the (D̃1E'←X̃1A1 '), the (F̃1E'←X̃1A1 '), and the (G̃1A2 ″←X̃1A1 ') absorption bands. In addition, new Rydberg members have been identified in nda1 '←1a2 ″D̃''1A2 ″←X̃1A1 ', where n > 3 has not been reported before as well as in nde″←1a2 ″F̃1E'←X̃1A1 ' and in nsa1 '←1a2 ″G̃1A2 ″←X̃1A1 '. The measured absolute photoabsorption cross sections have been used to calculate the photolysis lifetime of ammonia in the Earth's atmosphere (0-50 km).
Related Concept Videos
IR Frequency Region: X–H Stretching
IR Spectrum Peak Splitting: Symmetric vs Asymmetric Vibrations
NMR Spectroscopy Of Amines
IR Frequency Region: Fingerprint Region
Emission Spectra
Mass Spectrometry of Amines

