Absorption coefficients of molecular nitrogen have been measured with a photoelectric scanning technique using an intense, stabilized Hopfield heliumhyphen;continuum light source as background. These measurements differ from previous investigations where line sources were used as background. The measurements have been done with an instrumental bandwidth of 0.5 Aring; over a pressure range of 0.040 to 0.17 mm Hg using an absorption cell placed behind the exit slit of a vacuum monochromator. Corrections were made for the pressure gradient in the flowhyphen;absorption cell, for the scattered light, and for fluorescence. From 1000 to 796 Aring;, the first ionization threshold (N2+,X2Sgr;g+), a number of sharp, intense bands are present with no evidence of a dissociation continuum. Below 796 Aring;, the ionization continuum appears to rise slowly to 400 cmmdash;1at 742 Aring; (N2+,A2IIu), but this region is also crowded with many intense bands. Most of these appear to be strongly preionized. Between 742 Aring; and the threshold of theB2Sgr;u+state at 661 Aring;, the ionization continuum increases from roughly 400 to 780 cmmdash;1, and the prehyphen;ionized Hopfield Rydberg series is the main feature. At 661 Aring;, the absorption coefficient rises abruptly to 980 cmmdash;1and continues at approximately this constant value to 580 Aring;. The present results are compared whenever possible with previous measurements and discussed in relation to photohyphen;ionization measurements. Application of this data to calculation of absorption processes in the upper atmosphere is discussed.
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