Electronic and Vibrational Absorption Spectra of NH₂ in Solid Ne

Area of Science:

• Physical Chemistry
• Spectroscopy
• Astrochemistry

Background:

• Ammonia (NH3) photolysis is crucial for understanding chemical processes in various environments.
• Radical species like amidogen (NH2) and imidogen (NH) play significant roles in atmospheric and interstellar chemistry.
• Low-temperature matrix isolation techniques are vital for studying reactive intermediates.

Purpose of the Study:

• To investigate the formation and spectroscopic properties of amidogen (NH2) and imidogen (NH) radicals.
• To record and assign the electronic and infrared absorption spectra of NH2 and its deuterated variants (NHD, ND2).
• To determine precise vibrational frequencies for NH2 in a solid neon matrix.

Main Methods:

• Photolysis of ammonia (NH3) and its deuterated forms (ND3) in solid neon at cryogenic temperatures (near 4 K).
• Irradiation using tunable far-ultraviolet light from a synchrotron source.
• Recording electronic absorption spectra in the visible and near-ultraviolet regions.
• Identifying infrared absorption lines using isotopic substitution and analyzing vibration-rotational transitions.

Main Results:

• Amidogen (NH2) and imidogen (NH) radicals were successfully generated and detected.
• Electronic absorption spectra of NH2, NHD, and ND2 were obtained.
• Specific infrared absorption lines for NH2, corresponding to vibrational modes ν1 and ν2, were unambiguously assigned.
• The fundamental vibrational frequencies (000-000 transitions) for ν1 and ν2 of NH2 in solid neon were determined to be 3213.5 cm⁻¹ and 1494.6 cm⁻¹, respectively.

Conclusions:

• The study successfully characterized the spectroscopic signatures of amidogen radicals in a solid neon matrix.
• The precise determination of vibrational frequencies provides valuable data for identifying NH2 in extraterrestrial environments.
• This research contributes to a deeper understanding of ammonia photochemistry and the properties of radical species.