A Search for N2+ in Spectra of Comet C/2002C1 (Ikeya-Zhang)

TL;DR

This study used spectral observations of comet C/2002 C1 (Ikeya-Zhang) to search for N2+ ions, finding no definitive detection and discussing implications for early solar system conditions based on the non-detection.

Contribution

First high-resolution spectral search for N2+ in comet C/2002 C1, providing upper limits and analyzing implications for solar nebula composition.

Findings

N2+ was not definitively detected in high-resolution spectra.

Upper limit on N2+/CO+ ratio was established at 5.4×10^{-4}.

Detection in low-resolution spectra was likely telluric, not cometary.

Abstract

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.