Deep-Dive Guides · Molecular Spectroscopy
Physical Spectroscopy — the complete deep dive
One guide dense enough to take you from "I know Franck–Condon has something to do with UV" to CSIR-NET Part-C mastery.
Free extract — the opening section of the guide, in full.
0. How to use this guide — the universal triad
Do not memorise six unrelated spectroscopies. Memorise one template and instantiate it six times. For every technique ask:
| # | The question | What it comes from |
|---|---|---|
| 1 | Energy levels — what is En? | solve the model Hamiltonian (rigid rotor, harmonic oscillator, particle in box, spin in a field) |
| 2 | Selection rule — which Δn allowed? | the transition moment ⟨ψf|μ̂ (or α̂)|ψi⟩ must be ≠ 0 |
| 3 | Line positions — where do peaks appear? | ΔE = Ef − Ei = hν |
The gross vs specific selection rule — always separate them. A gross selection rule says whether a molecule is active at all in a technique (e.g. "must have a permanent dipole" for pure rotation; "dipole must change during the vibration" for IR; "polarizability must change" for Raman). A specific selection rule says which quantum-number jumps are allowed (ΔJ=±1, Δv=±1, etc.). Confusing the two is the single most common Part-C error.
Read the rest of this guide
The remaining 10 sections — Rotational (microwave) spectroscopy, Vibrational (IR) spectroscopy, Raman spectroscopy, Electronic (UV–Vis) spectroscopy and more — are part of ChemVidya Full Access, along with the other guides, the books, the study notes and 6,000+ practice questions with worked solutions.