The self-associating behavior of NH3 and ND3 in liquid xenon

• Self-association of NH3 and ND3 is observed in the infrared spectra of cryosolutions with liquid xenon.
• Least-squares fitting of polynomials to the data allows us to resolve spectral regions with overlapping absorbance bands.
• Least-squares fitting of polynomials yields accurate information on monomer and oligomer species present in the solutions.
• The least-squares fitting method shows an added value towards other methods often used.

In this study we report on the analysis of isothermal spectra of NH3 and ND3 solutions in liquid xenon at 203 K using newly developed and validated least-squares approaches to investigate the its self-associating behavior. For both species we observe clear dimer bands in the spectral area of the ν1+ν4, ν3+ν4 and ν1+ν2, ν3+ν2 combination bands. The analysis of the N−D stretching area, allows us to characterize clear contributions of dimers and trimers. The analysis of the NH stretching area is hampered by the occurrence of a time dependent band due to solid water traces during the experiments. For NH3 we also performed an investigation of the NH bending region, ν2, which demonstrated a small dimer absorption band. These obtained results compare well with literature data.

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