Transition Probability | Bransden & Joachain | 4.38 & 4.39 Dimension

In summary, at page 190 of Bransden & Joachain, there are two expressions for the transition probability, (4.38) and its absolute value squared in (4.39). The question raised is whether these two terms are dimensionally different. Upon further examination, it is found that every term from (4.38) appears squared in (4.39) except for the d\omega term, making it short by a factor of 1/sec. This inconsistency is also noted by Rodney Loudon in his book. However, he avoids this problem by taking the sum over frequencies first after squaring the amplitude. The question then arises of how this derivation is consistent.
  • #1
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At page 190 of Bransden & Joachain (see the page from http://books.google.com/books?id=i5...nsden,+Charles+Jean+Joachain&hl=da#PPA190,M1"), there are 2 expressions for the transition probability, (4.38) and it's absolute value squared in (4.39).
Is it just me or are the 2 term dimensionally different? Obviously everything from (4.38) is squared in (4.39) except the [itex] d\omega [/itex]. Hence they can't be the same dimensionally. How can this be right?
 
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  • #2
I am not sure what the question is, but they are both dimensionless. Probability doesn't have a unit.
 
  • #3
Cyosis: Yes they are supposed to be dimensionless, but I just looked at the difference between the 2 expressions.

Note that every term from (4.38) appears squared in (4.39) except for the [itex]d\omega [/itex] term which has the same power in both, hence (4.39) is short by a factor of 1/sec.
 
  • #4
In any case (4.38) is not the probability, it's the amplitude.
 
  • #5
But it's supposed to be dimensionless like the probability, hence must have the same dimensions.

EDIT:
Ok to make it more clear, then (4.38) has the form

[tex] c_b = \int_0^{\infty} f(\omega) \, d\omega [/tex]

while (4.39) has the form

[tex] |c_b|^2 = \int_0^{\infty} |f(\omega)|^2 \, d\omega [/tex]

which certainly can't be right. What's going on?
 
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  • #6
That's weird, it certainly does look dimensionally inconsistent, regardless of what cb represents.

I'm assuming ω means what it usually does and has units of s-1.
 
  • #7
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What is transition probability?

Transition probability refers to the likelihood of an atom or molecule undergoing a change in energy state, or "transitioning," from one quantum state to another. It is a fundamental concept in quantum mechanics and is often used to describe the behavior of electrons in atoms and molecules.

How is transition probability calculated?

Transition probability is typically calculated using mathematical equations, such as the Fermi's Golden Rule or the time-dependent Schrödinger equation. These equations take into account factors such as the initial and final quantum states, the energy difference between the states, and the interaction between the atom or molecule and its environment.

What is the significance of transition probability in quantum mechanics?

Transition probability plays a crucial role in understanding the behavior of subatomic particles, such as electrons, and their interactions with their surroundings. It also helps explain phenomena such as atomic and molecular spectra, which are used to identify and study the properties of different elements and compounds.

What are some factors that can affect transition probability?

The transition probability of an atom or molecule can be influenced by various factors, such as temperature, external electromagnetic fields, and collisions with other particles. The direction and intensity of the external field, as well as the energy and spin of the colliding particles, can also impact the probability of a transition occurring.

How is transition probability related to the uncertainty principle?

The uncertainty principle, a fundamental principle in quantum mechanics, states that it is impossible to simultaneously know the precise position and momentum of a particle. Transition probability is related to this principle because it describes the likelihood of a particle transitioning from one state to another, which is determined by its energy and momentum. The uncertainty principle also affects the accuracy with which we can measure the energy states of particles, which in turn affects the calculation of transition probabilities.

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