Fig. 1: Introduction of the nitrenium ions.
From: Generation and direct observation of a triplet arylnitrenium ion

a Electronic configurations of nitrenium ions: a closed-shell singlet state (1n2), an open-shell singlet state (1np), a second closed-shell singlet state (1p2), and an open-shell triplet state (3np), (b) proposed mechanism for the generation of triplet phenylnitrenium ion 32 (np): after excitation, the singlet excited state of 11 could go through the intersystem crossing (ISC) process to produce the triplet excited state of 31, which could generate the triplet nitrenium ion 32 through the N–N bond cleavage.