Question

Which of the following transitions between rotational energy levels is not allowed?

Select one:

a. J = 1 → J = 0

b. J = 0 ← J = 1

c. J = 1 ← J = 2

d. J = 1 ← J = 3

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Answer 1

Answer:

Explanation:

J=1«j=5

Answer 2

The correct option is d.

• In transitions between rotational energy levels, the selection rule for transition is ∆J = ±1.
• Here J is the rotational quantum number.
• So, for transition, J = 1 → J = 0 ∆J=1-0=1. So, it is allowed.
• For transition, J = 0 → J = 1 ∆J=0-1=-1. So, it is allowed.
• For transition, J = 1 → J = 2 ∆J=2-1=1. So, it is allowed.
• For transition, J = 1 → J = e ∆J=3-1=2. Thus in this transition ∆J is equal to 2. So, it is not allowed.