This is a proposal to search spectroscopically for nitrogen, a
 critical component in the chemistry of the interstellar medium.
 We will use the ISO-SWS in SWS01 and SWS06 modes to observe source
 of high extinction in molecular clouds to search for the
 fundamental absorption band of alpha phase N2 ice at 2328.1 cm-1
 (4.295 micrometers).  This band consists of two principal
 components, one a sharp spike at the noted frequency, and a
 broader component of much larger integrated absorbance extending
 from ~2320 to 2480 cm-1 (4.032- 4.310 micrometers).  We will use
 data from our laboratory on the temperature sensitivity of the
 relative strengths of the two band components for an independent
 indication of the temperature of the N2-bearing grains.  We will
 also use our laboratory data on mixtures of other ices
 (e.g., CO2, CO) with N2 in the interpretation of the abundance
 of the nitrogen. ISO is required for these observations because
 the N2 band occurs at a frequency that is entirely blocked from
  Earth-based telescopes by telluric CO2 absorption.