Terahertz spectroscopy of water in its second triad

Abstract

Terahertz absorption spectroscopy was employed to measure rotational transitions of water in its second triad 3ν2,ν1+ν2 and ν3+ν2. Highly excited water molecules were created with a DC discharge, which allowed observation of transitions with lower state energies up to 5939cm−1. In the 0.5–2.0THz region, 38 pure rotational transitions in the second triad were observed with MW accuracy for the first time. Additionally, 91 new rotational and ro-vibrational transitions within the ground state, ν2, and the first triad (2ν2,ν1 and ν3) were measured with multiplier chains covering the 1.3–2.0THz region.