Q109 · CSIR-NET Chemistry, June 2011

Paper: CSIR-NET June 2011 · Subject: Physical Chemistry · Chapter: Group Theory · Topic: Character Tables · Marks: 2 · Difficulty: Medium

Refer to the character table of the point group $\mathrm{C}_{3 \mathrm{V}}$ given above. Find which of the following transition is forbidden
(a)$\mathrm{a}_{1} \leftrightarrow \mathrm{a}_{1}$
(b)$\mathrm{a}_{1} \leftrightarrow \mathrm{e}$
(c)$\mathrm{a}_{2} \leftrightarrow \mathrm{e}$
(d)$\mathrm{a}_{1} \leftrightarrow \mathrm{a}_{2}$
Answer
Answer: D ✓ checked by 4AB · confidence high
Explanation
In C₃v the dipole components span A₁ (z) and E (x, y). A₁ × A₂ = A₂ contains neither A₁ nor E, so a₁ → a₂ is forbidden; the other three products contain an allowed representation.

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