Number of ESR Lines Expected

Electronic Transition Expected in Methyl Radical, Hydrogen atom and NO Molecule

Electronic Transition Expected in Methyl Radical

Methyl radical has one unpaired electron and ¹²C has zero I value whereas H nuclei have 1/2 I value. Hence the number of ESR lines are four for methyl radical.

ESR Lines = 2nI + 1
or, ESR Lines = 2 x (3x1/2) + 1 = 4
Intensity Ratio = 1:3:3:1

Electronic Transition Expected in Methyl Radical

H atom has one unpaired electron and its I value is 1/2. Hence the number of ESR lines are two.

ESR Lines = 2nI + 1
or, ESR Lines = 2 x (1x1/2) + 1 = 2

Electronic Transition Expected in NO Molecule

NO molecule has one unpaired electron so the expected number of ESR line is one but actually it shows three esr peaks with peak intensity ratio 1:2:1. The ¹⁶O has zero I value. The signal splitts due to coupling with N-nucleus which has nuclear spin (I) value one.

Hence, the number of lines or peaks-
2nI + 1 = 2 x (1 x 1) + 1 = 3

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