Paper: CSIR-NET June 2011 · Subject: Physical Chemistry · Chapter: Molecular Spectroscopy · Topic: Molecular Spectroscopy – General · Marks: 2 · Difficulty: Medium
A molecule, AX, has a vibrational energy of $1000 \mathrm{cm}^{-1}$ and rotational energy of $10 \mathrm{cm}^{-1}$. Another molecule, BX, has a vibrational energy of 400 cm-1 and rotational energy of $40 \mathrm{cm}^{-1}$. Which one of the following statements about the coupling of vibrational and rotational motion is true?
(a)The coupling is stronger in BX.
(b)The coupling is stronger in AX.
(c)Magnitude of coupling is same in both AX and BX.
(d)There is no coupling in both AX and BX
Answer
Answer: A ✓ checked by 4AB · confidence high
Explanation
Rotation–vibration coupling grows with the ratio B/ω: BX (40/400 = 0.1) couples far more strongly than AX (10/1000 = 0.01).