  We report low- and high-resolution spectra of comet C/2002 C1 (Ikeya-Zhang)
from McDonald Observatory. The comet had a well-developed ion tail including
CO+, CO2+, CH+, and H2O+. We used our high-resolution spectra to search for
N2+. None was detected and we placed upper limits on N2+/CO+ of 5.4 times
10^{-4}. N2+ was detected in the low-resolution spectra but we show that this
emission was probably telluric in origin (if cometary, we derive N2+/CO+ = 5.5
times 10^{-3}, still very low). We discuss the implications for the conditions
in the early solar nebula of the non-detection of N2+. These depend on whether
the H2O ice was deposited in the amorphous or crystalline form. If H2O was
deposited in its crystalline form, the detection of CO+ but not N2+ has
implications for H2O/H2 in the early solar nebula.
