Q25 · CSIR NET Chemistry, June 2015
Paper: CSIR NET June 2015 · Subject: Physical Chemistry · Chapter: Atomic and Molecular Term Symbol · Topic: Selection Rules · Marks: 2 · Difficulty: Easy
The electric-dipole allowed transition among the following is
(a)${ }^{3} \mathrm{S} \rightarrow{ }^{3} \mathrm{D}$
(b)${ }^{3} \mathrm{S} \rightarrow{ }^{3} \mathrm{P}$
(c)${ }^{3} \mathrm{S} \rightarrow{ }^{1} \mathrm{D}$
(d)${ }^{3} \mathrm{S} \rightarrow{ }^{1} \mathrm{F}$
Answer
Answer: B ✓ checked by 4AB · confidence high
Explanation
Electric-dipole selection rules: ΔS = 0 and ΔL = ±1. Only ³S → ³P satisfies both; ³S → ³D has ΔL = 2 and the singlet targets break ΔS = 0.
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