WATER ON THE SUN: A NEW SPECTROSCOPIC PARADIGM

Sunspot infrared absorption spectra with $T \sim 3000^\circ$ and $750 \leq \bar{\nu} \leq 1010 cm^{-1}$ have recently been $reported^{a}$. The spectra are highly congested ($\sim$ 50 lines per $cm^{-1}$) with spectral lines thought to be due to water. Traditional perturbation theory is inadequate for analysing this problem. Instead we employ full variational solutions of the problem which go beyond the standard Born-Oppenheimer approximation. This treatment leads to vibration-rotation quantum number assignments for individual lines (none of which had been previously assigned). Furthermore we attribute many more spectral lines to water than could be achieved using previous theory or $experiment^{g}$. In particular we assign transitions involving rotational levels in the ground state and first few vibrational states up to 22,000 $cm^{-1}$ above the ground state, about double that previously known and approximately halfway to dissociation. In addition we assign levels with $K_{a}$ as high as 32 compared to the previous maximum of 20. We find previously unobserved and unanticipated spectroscope characteristics of water. These characteristics will be present in other hot water spectra found in flames, rocket plumes, cool stellar atmospheres and elsewhere, as well as in the spectra of other hot molecules. The approach applied here thus represent a paradigm shift in the theory of polyatomic molecular spectroscopy which we expect will be widely followed in all future treatments of the spectra of hot molecules.

Description

$^{g}$L. Wallace, et al Science 268, 1155-1158 (1995).
Author Institution: Department of Physics Astronomy, University College London; Department of Chemistry, University of Waterloo; National Optical Observatories, POBOX 26732 Tucson, AZ

URI

http://hdl.handle.net/1811/13833

Collections

Abstracts of OSU International Symposium on Molecular Spectroscopy 1990-1999

Full item page

Knowledge Bank