The vibrational frequency and anharmonicity constant of an alkali halide are 300 cm⁻¹ and 0.0025 respectively. The positions (in cm⁻¹) of its fundamental mode and first overtone are respectively.

Q92 · CSIR-NET Chemistry, December 2012

Paper: CSIR-NET December 2012 · Subject: Physical Chemistry · Chapter: Molecular Spectroscopy · Topic: Vibrational · Marks: 2 · Difficulty: Medium

The vibrational frequency and anharmonicity constant of an alkali halide are $300 \mathrm{cm}^{-1}$ and 0.0025 respectively. The positions (in $\mathrm{cm}^{-1}$ ) of its fundamental mode and first overtone are respectively.

(a)300,600

(b)$298.5,595.5$

(c)$301.5,604.5$

(d)290, 580

Answer

Answer: B ✓ checked by 4AB · confidence high

Explanation

Fundamental ω_e(1 − 2χ_e) = 300 × 0.995 = 298.5; first overtone 2ω_e(1 − 3χ_e) = 600 × 0.9925 = 595.5 cm⁻¹.

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