Electron Densities and Nitrogen Abundances in Ionized Gas Derived Using
  [NII] Fine-structure and Hydrogen Recombination lines
  We present a method for deriving the electron density of ionized gas using
the ratio of the intensity of the [NII] 205um line to that of Hydrogen radio
recombination lines (RRL). We use this method to derive electron densities of
21 velocity components in 11 lines of sight through the Galaxy, including the
Galactic center. We observed, at high--spectral resolution, the [NII] 205um
line with the Herschel/HIFI and SOFIA/GREAT instruments and the radio
recombination lines with the Green Bank Telescope and the NASA Deep Space
Network Deep Space Station 43 (DSS--43) telescope. We find typical electron
densities between 6 to 170 cm^-3, which are consistent with those derived at
low spectral resolution using the [NII] 205um/122um line ratio with
Herschel/PACS on a larger sample of sight lines in the Galactic plane. By
matching the electron densities derived from the [NII] 205um/RRL intensity
ratio and the [NII] 122um/205um intensity ratio, we derive the nitrogen
fractional abundance for most of the velocity components. We investigate the
dependence of the N/H ratio with Galactocentric distance in the inner Galaxy
(R_gal<6 kpc, which is inaccessible in optical studies due to dust extinction.
We find that the distribution of nitrogen abundances in the inner galaxy
derived from our data has a slope that is consistent to that found in the outer
Galaxy in optical studies. This result is inconsistent with some suggestions of
a flatter distribution of the nitrogen abundance in the inner galaxy.
