Terahertz absorption spectrum of D2O vapor

The absorption spectrum of D2O vapor from 0.2 to 2.0 THz (6.7–67 cm−1) which is associated with rotational modes was measured at one atmosphere using terahertz time-domain spectroscopy (THz-TDS). The linewidth and collisional dephasing times were measured for 26 pure rotational transitions in the ground vibrational state (0 0 0). The temperature dependence of the linewidth (Δν) behaves as Δν ∼ T−3/4 and the linewidth decrease with increasing temperature is attributed to the 1/r6 force of interaction between colliding D2O molecules.