Amazing explanation! Thank you, i have a question that i couldn't understand searching in internet: What is the difference between Raman Resonance and Fluorescence? the only difference i can see is that in fluorescense the part of no radiative deccay after absorption of a photon is from vibrational state in E1 to a v0 of E1, and then the fluorescense is emmited by radiative deccay to basal level E0, in Raman (here) i only see deccay from v0 of E1 to a vibrational level (different of 0) in E0, is that the only difference?
"What is the difference between Raman resonance and fluorescence?" The principal difference is that Raman scattering of light involves a transition between molecular vibrational states, whereas fluorescence involves a transition between molecular electronic states and the emission of a photon. In both cases, the molecule is initially excited to an electronic state above the ground electronic state. If the molecule returns to the ground electronic state through the emission of a photon, that emission is called fluorescence. However, if the molecule returns to the first excited vibrational state of the ground electronic state and emits a photon whose energy is less than the exciting energy by the differences in energies of the ground and excited vibrational states, then that is called Raman scattering.
@@dtuschel First of all, thank you very much for your answer and for your time! According to what I understood from your answer, in both cases a lower energy photon is emitted. However, to differentiate between the two cases, in fluorescence: the loss of energy due to non-radiative decay occurs due to the passage from a higher vibrational state within the excited state to the base vibrational state of the same excited state and then radiative decay (fluorescence) leads to the basal state in its minimum vibrational state. On the other hand, in resonant Raman: First the radiative decay (scattering) occurs from the excited state to the ground state at a higher vibrational level, and then the loss of energy by non-radiative decay to the vibrational minimum state. Is it so? Thank you again, greetings from Uruguay! You have great teaching skills
You have described the Raman and fluorescence processes accurately and I think that you have the correct understanding of these processes. I wish you success in your continuing studies and thank you for your kind words regarding my teaching.
@@dtuschel Thank you very much, you cleared my head! And good luck to you too, your passion for science is remarkable, it's not easy to find a researcher and teacher on youtube who takes the time to answer like you do, for free. Big hug!
In resonant Raman the increasing energy can be seen from diagram, how can it lead to intensification in intensity which is dependent on population of electrons?
This is a frequently asked and good question. The answer to it is rather complicated and somewhat lengthy involving quantum mechanics and, in particular, the Kramers Heisenberg Dirac equation. I provide a complete answer to your question in my publication titled "Exploring Resonance Raman Spectroscopy" in Spectroscopy, 33(12) 12(2018). Your question is answered beginning on the bottom of p. 13.
Dear sir, thank you for humble response .I will read it... Please make a detailed video on SERS, I am a new PhD student and my project is on High temperature SERS.... Can I get some help from you regarding developing a good understanding on SERS
If you require personal assistance understanding SERS, you should obtain that from your research adviser or other colleagues at your university who have in depth knowledge of Raman spectroscopy.
The enhancement of signal strength occurs only for those Raman active vibrational modes that couple to the electronic transition induced by the laser. The laser wavelength must match that of the molecule's absorption band for resonance to occur. I explain this in more detail between 2:10 and 3:40 of the video. To understand why the intensity increases, we must turn our attention to the denominator in the Kramers Heisenberg Dirac equation. The closer the laser frequency is to that of an electronic transition the smaller the denominator becomes leaving only the damping constant, iΓ. Were it not for the addition of the damping constant, the denominator could in principle go to zero when the laser frequency equaled that of the electronic transition and the Raman polarizability would go to infinity. Of course, that doesn’t happen and actual resonance enhancements over normal Raman scattering are typically 10 to the 4th power to 10 to the 6th power.
Also, you can find a discussion of the Kramers Heisenberg Dirac equation and its relevance to resonant Raman signal strength in my Spectroscopy publication (www.spectroscopyonline.com/view/exploring-resonance-raman-spectroscopy) titled Exploring Resonance Raman Spectroscopy.
Wonderful presentation! Thanks for sharing!
The complexity of the physical world is truly daunting and humbling. In my 5th decade I seem only to be *beginning* to understand....
extremely useful and very clearly explained. Thank you
Glad it was helpful!
Thank you so much.
Amazing explanation! Thank you, i have a question that i couldn't understand searching in internet:
What is the difference between Raman Resonance and Fluorescence? the only difference i can see is that in fluorescense the part of no radiative deccay after absorption of a photon is from vibrational state in E1 to a v0 of E1, and then the fluorescense is emmited by radiative deccay to basal level E0, in Raman (here) i only see deccay from v0 of E1 to a vibrational level (different of 0) in E0, is that the only difference?
"What is the difference between Raman resonance and fluorescence?" The principal difference is that Raman scattering of light involves a transition between molecular vibrational states, whereas fluorescence involves a transition between molecular electronic states and the emission of a photon. In both cases, the molecule is initially excited to an electronic state above the ground electronic state. If the molecule returns to the ground electronic state through the emission of a photon, that emission is called fluorescence. However, if the molecule returns to the first excited vibrational state of the ground electronic state and emits a photon whose energy is less than the exciting energy by the differences in energies of the ground and excited vibrational states, then that is called Raman scattering.
@@dtuschel
First of all, thank you very much for your answer and for your time!
According to what I understood from your answer, in both cases a lower energy photon is emitted.
However, to differentiate between the two cases, in fluorescence: the loss of energy due to non-radiative decay occurs due to the passage from a higher vibrational state within the excited state to the base vibrational state of the same excited state and then radiative decay (fluorescence) leads to the basal state in its minimum vibrational state.
On the other hand, in resonant Raman: First the radiative decay (scattering) occurs from the excited state to the ground state at a higher vibrational level, and then the loss of energy by non-radiative decay to the vibrational minimum state.
Is it so?
Thank you again, greetings from Uruguay! You have great teaching skills
You have described the Raman and fluorescence processes accurately and I think that you have the correct understanding of these processes. I wish you success in your continuing studies and thank you for your kind words regarding my teaching.
@@dtuschel Thank you very much, you cleared my head! And good luck to you too, your passion for science is remarkable, it's not easy to find a researcher and teacher on youtube who takes the time to answer like you do, for free. Big hug!
new subscriber!
Thank you sir this was really helpful
I am glad that you found the explanation helpful.
In resonant Raman the increasing energy can be seen from diagram, how can it lead to intensification in intensity which is dependent on population of electrons?
This is a frequently asked and good question. The answer to it is rather complicated and somewhat lengthy involving quantum mechanics and, in particular, the Kramers Heisenberg Dirac equation. I provide a complete answer to your question in my publication titled "Exploring Resonance Raman Spectroscopy" in Spectroscopy, 33(12) 12(2018). Your question is answered beginning on the bottom of p. 13.
Dear sir, thank you for humble response .I will read it... Please make a detailed video on SERS, I am a new PhD student and my project is on High temperature SERS.... Can I get some help from you regarding developing a good understanding on SERS
If you require personal assistance understanding SERS, you should obtain that from your research adviser or other colleagues at your university who have in depth knowledge of Raman spectroscopy.
Sir where are you?
Where am I? I am in Wisconsin.
why does resonance enhanced Raman spectroscopy produced increased intensity ?
The enhancement of signal strength occurs only for those Raman active vibrational modes that couple to the electronic transition induced by the laser. The laser wavelength must match that of the molecule's absorption band for resonance to occur. I explain this in more detail between 2:10 and 3:40 of the video. To understand why the intensity increases, we must turn our attention to the denominator in the Kramers Heisenberg Dirac equation. The closer the laser frequency is to that of an electronic transition the smaller the denominator becomes leaving only the damping constant, iΓ. Were it not for the addition of the damping constant, the denominator could in principle go to zero when the laser frequency equaled that of the electronic transition and the Raman polarizability would go to infinity. Of course, that doesn’t happen and actual resonance enhancements over normal Raman scattering are typically 10 to the 4th power to 10 to the 6th power.
Also, you can find a discussion of the Kramers Heisenberg Dirac equation and its relevance to resonant Raman signal strength in my Spectroscopy publication (www.spectroscopyonline.com/view/exploring-resonance-raman-spectroscopy) titled Exploring Resonance Raman Spectroscopy.