Enhancing NIR Spectroscopy: Revealing Rovibrational Details of Stellar and Exoplanetary Atmospheres

In 1-dimensional spectroscopy, rovibrational movements of organic, floppy gas molecules produce spectra that are heavily congested. This is caused by the overlapping overtones of similar frequencies. This congestion is especially worse in the near-infrared region, which results in illegible spectra. Unfortunately, this means a huge section of rovibrational spectra is neglected despite it containing important information about molecular characteristics. Coherent 2-dimensional spectroscopy offers a way to clear up spectra by isolating rovibrational bands and “stretching” out the peaks. Four wave mixing signals are generated by broadband NIR (ω₁) and narrowband mid-IR (ω₂) laser pulses. The resulting 2-dimensional rovibrational patterns reveal information about rovibrational symmetries of coupled modes. This technique could be applied to existing NIR spectrometers. In particular, the James Webb Space Telescope regularly collects NIR data that cannot be interpreted and could reveal important details about stellar and exoplanetary atmospheres.