Neglect rotation–vibration interaction in HF. Find the R-branch IR line starting at J = 4 in cm⁻¹, nearest integer. B = 19.35 cm⁻¹ and band origin is 4138.52 cm⁻¹.
An R-branch transition has ΔJ = +1. With equal rotational constants in the two vibrational levels, $\tilde\nu_R(J)=\tilde\nu_0+2B(J+1)$. Thus $4138.52+2(19.35)(5)=4332.02$ cm⁻¹, or 4332.
More Spectroscopy: Atomic spectroscopy; Russell-Saunders coupling; Term symbols and spectral details; origin of selection rules. Rotational, Vibrational, Electronic and Raman spectroscopy of diatomic and simple polyatomic molecules. Line broadening and line widths; simple properties of Gaussian and Lorentzian line shapes. Molecular spectroscopy: Absorbance, Beer- Lambert’s law, Einstein’s coefficient, Jablonski diagram. Relationship of transition moment integral with molar extinction coefficient and oscillator strength. Basic principles of Nuclear Magnetic Resonance: Gyromagnetic ratio; Chemical shift, nuclear coupling. questions
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