The set of allowed electronic transitions among the following is:(A) $^{4}\Sigma \rightarrow {}^{2}\Pi$ (B) $^{3}\Sigma \rightarrow {}^{3}\Pi$ (C) $^{1}\Delta \rightarrow {}^{1}\Delta$ (D) $^{2}\Pi \rightarrow {}^{2}\Pi$ (E) $^{3}\Sigma \rightarrow {}^{3}\Delta$
(a)A, B, E
(b)A, C, E
(c)B, C, D
(d)C, D, E
Answer
Answer: C ✓ checked by 4AB · confidence high
The source book printed no answer; this one was worked out and checked — see the explanation.
Explanation
Selection rules: ΔS = 0 and ΔΛ = 0, ±1. (A) ⁴Σ→²Π and (E) ³Σ→³Δ (ΔΛ = 2) are forbidden; B, C and D are allowed.