Our manuals indicate a lack of emissivity data for oxidized Titanium at 1um, but include data for unoxidized Ti (at higher temperatures would need to be in a vacuum.
Furthermore, our website states "not recommended" for oxidized Titanium at 1um.
The reason for this is not known. It may be purely due a lack of data, or based some other reason like e-slope instability.
It is more likely due to a lack of data.
There is a published paper for Titianium and Zirconium emissivity testing includes the comment "The emissivities measured in vacuum were quite large indication a possible contamination/oxidization".
It may therefore, not be unreasonable to make the assumption that this paper is useful as an indication of general emissvity: