New progress in spectroscopy of ammonia in the infrared 1.5μm range using evolution of spectra from 300 K down to 122 K

Analysis of the temperature dependence of the ratio of the intensity of two assigned and unassigned lines enables the determination of the most probable energy of the lower state of the unassigned transition. Such a new procedure has been applied to transitions of ammonia in the range 6626.0-6668.5 cm−1 between 122 K and 300 K. This represents a first step in the considerable task of the assignment of the complete 1.5μm infrared spectral range.

► Ammonia spectra have been recorded from 300 K to 130 K at 1.5μm. ► Assignments in this range are partially known. ► Evolution of line relative intensities gives lower state of unassigned transitions. ► This information is quasi exhaustive in a given range. ► It represents a significant step towards global assignment.