Velocity-Resolved Observations of H[alpha] Emission From Comet C/1995 O1 (Hale-Bopp)

We present hydrogen Balmer-α spectra of comet C/1995 O1(Hale-Bopp) recorded on 5 nights from 1997 February 1 to April 19 by ahigh-resolution (Δ v = 5 km s^sup -1^) Fabry-Pérot spectrometer for a4'.1 (2.7 × 10^sup 5^ km) FOV centered 5' sunwardof the nucleus. The Hα line profile is an important diagnostic ofphotolytic heating in cometary atmospheres. Extraction of the spectrafrom the Fabry-Pérot ring images was complicated by obscuration of the telescope FOV due to Hale-Bopp's low elevation, but the measuredH-α line widths of 11-13 km s^sup -1^ (FWHM) are insensitive to the spectral extraction technique. The line widths are consistent withestimates derived from a successful model of Hale-Bopp's hydrogenLyman-α coma assuming the inner coma is opaque to Hα. Wediscuss methods for improving the spectral extraction technique andderiving a precise instrument profile which will allow the detailedshape of the line profile to constrain coma models.[PUBLICATION ABSTRACT]