2012ApJ...750..127L

Raman scattering of He II line photons with atomic hydrogen is important in studying the mass loss processes in many symbiotic stars and a number of young planetary nebulae. We calculate the scattering cross sections and branching ratios associated with the Raman scattered He II λ4332 feature formed through inelastic scattering of He II λ949 with a hydrogen atom. At the line center of He II λ949, the total scattering cross section is computed to be σ_tot= 2.5x10^–22 cm2, and the branching ratio into the level 2s is 0.12. We also present a high-resolution spectrum of the symbiotic star V1016 Cygni obtained with the 1.8 m telescope at Mt. Bohyun to investigate the Raman scattering origin of the broad feature blueward of He II λ4338. Based on the atomic calculation, we perform Monte Carlo calculations for the line formation. The scattering region is assumed to be a part of a uniform spherical shell that subtends a solid angle ΔΩ=π steradian with a neutral column density N_HI=1.0x10²¹/cm2. By adding a far-UV continuum around He II λ949 normalized by the equivalent width of He II λ949 to be 2.3 Å, we obtain a good fit for both the Raman scattered He II λ4332 and the broad wings around Hγ. Our analysis of the Raman feature blueward of Hγ in V1016 Cyg is consistent with the previous study of the Raman features blueward of Hα and Hβ by Jung and Lee.