I am also considering using ammonia vapour which has a similar ionisation energy to nitrogen.
According to NIST data, ammonia (gas) have a ionisation energy of 10.2 eV, much lower than N2 (15.5 eV).
THF is particularly useful for electrolysing materials subject to forming hydroxides in water - as many of the lanthanides I want to test are.
Interesting... I didn't know THF and this specific application. Can you dissolve ionic salts in THF? If so, probably this can be used to deposit alkali metals on the cathode avoiding their dissolution as hydroxides (?)