WATER ON THE SUN - LINE ASSIGNMENTS BASED ON VARIATIONAL CALCULATIONS

The infrared spectrum of hot water observed in a sunspot has been assi gned. The high temperature of the sunspot, (3200 K) gave rise to a hig hly congested pure rotational spectrum in the 10-micrometer region tha t involved energy levels at least halfway to dissociation, Traditional spectroscopy, based on perturbation theory, is inadequate for this pr oblem. Instead, accurate variational solutions of the vibration-rotati on Schrodinger equation were used to make assignments, revealing unexp ected features, including rotational difference bands and fewer degene racies than anticipated. These results indicate that a shift away from perturbation theory to first. principles calculations is necessary in order to assign spectra of hot polyatomic molecules such as water.