Find units of transition dipole moment

In summary, there are two different formulas for the relationship between oscillator strength and transition dipole moment, with different values for the constants and units of measurement. It is important to use the correct formula in order to calculate the transition dipole moment accurately.
  • #1
sshrestha
1
0
I have been trying to figure out which formula for the relationship between oscillator strength and transition dipole moment is correct.

Wiki had the following formula:

http://photonicswiki.org/index.php?title=Transition_Dipole_Moment

f = 4.703 \times 10^{29} \bar{v} \mu^{2}_{ge}\,\!

where

\bar{v}\,\! is the mean absorption frequency of the band in cm–1

\mu^{2}_{ge}\,\!, refers to the square of the transition dipole moment between the ground state and the excited state.

What I am unsure about is how they got the value of the constants and the units for it.

In another reference I had this formula:

f =[(8*pi*massofelectron)/(3*planck's const*electric)charge^2)] *vbar*u^2

When I calculate the constant using this formula I get 4.49 * 10^41. Moreover I am also confused about whether vbar is frequency or wavenumber. Since wavenumber is in cm^-1 the units don't cancel out and f is no longer dimensionless. Has anyone done this kind of calculation?

The values that I have in order to calculate the transition dipole moment is energy and f.

I use E = Planck's const*frequency to get frequency and then c= frequency*wavelenth to get the wave number and plug it in the equation. In either case the value I get is very off. Can you please help me figure out where I am missing the point?
 
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  • #2
The correct formula for the relationship between oscillator strength and transition dipole moment is:f = [ (2*π*m*e)/(3*h*ε₀) ] *νₐᵣ*μ²ᵍᵉwhere:f is the oscillator strength,m is the mass of an electron,e is the charge of an electron,h is Planck's constant,ε₀ is the permittivity of free space,νₐᵣ is the mean absorption frequency in cm⁻¹, andμ²ᵍᵉ is the square of the transition dipole moment.
 

1. What is a transition dipole moment?

A transition dipole moment is a measure of the strength and direction of the electric dipole moment between two electronic states of a molecule. It is a vector quantity that describes the change in the distribution of electron density during a transition between two energy levels.

2. Why is it important to find units of transition dipole moment?

The units of transition dipole moment are important because they provide a standard way to measure and compare the strength of different dipole moments. This is especially useful in the study of molecular spectroscopy, where transition dipole moments are used to calculate the intensity of absorption or emission spectra.

3. How is the transition dipole moment calculated?

The transition dipole moment is calculated by taking the product of the electronic charge, the distance between the two electronic states, and the difference in the dipole moment between the two states. This calculation yields a value with units of charge times distance, such as Debye (D) or Coulomb-meter (C m).

4. What are the common units of transition dipole moment?

The most commonly used units of transition dipole moment are Debye (D) and Coulomb-meter (C m). However, other units such as atomic units (a.u.) and meter-kilogram-second (mks) units are also used in some scientific fields.

5. How can I convert between different units of transition dipole moment?

To convert between units of transition dipole moment, you can use conversion factors or online unit converters. For example, 1 Debye is equal to 3.33564 x 10^-30 Coulomb-meter. It is important to note the units when converting, as the values may differ depending on the units used.

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