Forbidden Transition in the Spectrum of Interstellar Ionized Titanium

Abstract

AN exploration of the ultra-violet spectra of a number of stars has recently been undertaken in collaboration with Dr. Walter S. Adams, using the aluminized mirror of the 100-inch telescope, a new grating of high efficiency ruled by B. W. Wood on an aluminized Pyrex disc, and an off-axis Schmidt camera¹ of 32 inches focal length which gives, in the second order, a scale of 10.2 A. per mm. Two sharp lines at 3241.99 and 3383.78 the appearance of which suggests an interstellar origin have been photographed in the spectra of five stars of early type: Persei (O_e5), Orionis (O_e5), X Aurigae (B1), X² Orionis (B2) and 55 Cygni (B2). The interstellar sodium pair (3s²S – 4p²p⁰) at 3302.38 and 3302.98 were used as standards in determining the wavelengths of these lines.