  We report measurements of the optical properties of the 1042 nm transition of
negatively-charged Nitrogen-Vacancy (NV) centers in type 1b diamond. The
results indicate that the upper level of this transition couples to the
m_s=+/-1 sublevels of the {^3}E excited state and is short-lived, with a
lifetime <~ 1 ns. The lower level is shown to have a temperature-dependent
lifetime of 462(10) ns at 4.4 K and 219(3) ns at 295 K. The light-polarization
dependence of 1042 nm absorption confirms that the transition is between
orbitals of A_1 and E character. The results shed new light on the NV level
structure and optical pumping mechanism.
