4AB › Chemistry PYQ › CSIR-NET › December 2013 › Q97Q97 · CSIR-NET Chemistry, December 2013 Paper: CSIR-NET December 2013 · Subject: Physical Chemistry · Chapter: Group Theory · Topic: Character Tables · Marks: 2 · Difficulty: Medium
The transition that is allowed by x-polarized light in trans-butadiene is (The character table for $\mathrm{C_{2h}}$ is given below) $\mathrm{C_{2h}}$ E $\mathrm{C_2}$ i $\sigma_h$ $\mathrm{A_g}$ 1 1 1 1 $R_z, x^2, y^2, z^2, xy$ $\mathrm{B_g}$ 1 -1 1 -1 $R_x, R_y, xz, yz$ $\mathrm{A_u}$ 1 1 -1 -1 z $\mathrm{B_u}$ 1 -1 -1 1 x, y
(a) ${ }^{1} \mathrm{A}_{\mathrm{u}} \leftrightarrow{ }^{1} \mathrm{A}_{\mathrm{u}}$
(b) ${ }^{1} \mathrm{A}_{\mathrm{u}} \leftrightarrow{ }^{1} \mathrm{B}_{\mathrm{g}}$
(c) ${ }^{1} \mathrm{B}_{\mathrm{u}} \leftrightarrow{ }^{1} \mathrm{B}_{\mathrm{g}}$
(d) ${ }^{3} \mathrm{B}_{\mathrm{g}} \leftrightarrow{ }^{1} \mathrm{A}_{\mathrm{g}}$
Answer Answer: B ✓ checked by 4AB · confidence high
Explanation In C₂h, x transforms as B_u. A transition is x-allowed if Γ_i × B_u × Γ_f contains A_g: A_u × B_u × B_g = A_g, so ¹A_u → ¹B_g is allowed (b); the others give A_u, B_u or a spin change.
← Q96 · All questions in this paper · Group Theory chapter list · Q98 → Study loop for Group Theory
Open in whiteboard · Browse this chapter in the app