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Indian Forest Service (Mains)

Chemistry optional

  • 2 papers
  • 200 marks each
  • 3 h per paper

Paper II covers organic chemistry and spectroscopy.

Indian Forest Service (Mains), Chemistry optional · 2025 · Paper II

Q8(b)(ii). Hot-band population in iodine

Question

For I₂ at 300 K, use equilibrium wavenumber 215 cm⁻¹ and xₑ = 0.003 to find the first hot-band intensity relative to the fundamental.

Answer in brief

The usual population-only estimate is N₁/N₀ ≈ 0.359 (about 36%); an actual band-intensity ratio also depends on transition strengths and the spectroscopic process.

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Topic notes: vibrational and electronic spectra (force constant, isotope effect, overtones, Franck–Condon), with every Civil Services, IFoS and Geo-Scientist PYQ →

Covershot bandanharmonicity constantBoltzmann populationvibrational spectroscopy of I₂anharmonic oscillator

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