Intersystem Crossing of 2-Methlypyrazine Studied by Femtosecond Photoelectron Imaging
Round 1
Reviewer 1 Report
The manuscript "Intersystem Crossing of 2-Methlypyrazine Studied by Femtosecond Photoelectron Imaging" is good and novel work.
However, there are a few modifications suggested which should be incorporated into the manuscript to make it readable to wide researchers.
1. The abstract need to be modified completely the authors have straight away discussed the material and the technique. There should be a proper opening statement and significance.
2. The authors have explored singlet and triplet states, they have discussed about the lifetime but not the energies/positions of these states. Its is required that these states should be depicted by a model with defined positions.
3. The pulse energy of 4.5 MJ is too much it seems its a typographical error it should be 4.5 mJ.
4. There are many spelling mistakes which should be corrected.
5. All transitions happening in less than 100 fs should have an explanation that how they are determined since the pulse width is 100 fs and the cross-correlation between pump and probe is 200fs so any measurement below 200fs should be either extrapolated or determined through some modelling.
6. A model depicting the singlet and triplet states along with ground state position should be provided.
Author Response
Response to Reviewer 1 Comments
Dear Editor,
Thank you, the referees, and the production editor for your patience and so many helpful suggestions on our paper. According to the referee’s useful suggestions, we have carefully revised our manuscript.
The following is our reply to the comments, which is based on some of our major revisions of the content.
Manuscript No.: molecules-1911711
Point 1: The abstract need to be modified completely the authors have straight away discussed the material and the technique. There should be a proper opening statement and significance.
Response 1: Thank you very much for your instruction. We followed your guidance with a description of the meaning in the introduction. On lines 26-28 of the introductory section. (Page1, Line26-28)
Biomolecules are excited to electronic excited states after absorbing ultraviolet light, which can lead to some excited state photochemical processes that are harmful to living organisms [1-2]. Intersystem crossing and internal conversion are the primary excited-state relaxation pathways essential for many biological processes, such as photosynthesis and DNA self-repair. Hence, it is important to study electron relaxation dynamics in these non-adiabatic processes [3-4]. Because molecules can be ionized from arbitrary excited states having various multiplicities, there is a need to observe levels of dark states in real time via intersystem crossing (ISC) [5]. Quantum-yield and fluorescence measurements can reveal non-adiabatic dynamical information. However, there is an urgent need for a comprehensive method to elucidate the entire dynamics.
Point 2: The authors have explored singlet and triplet states, they have discussed about the lifetime but not the energies/positions of these states. Its is required that these states should be depicted by a model with defined positions.
Response 2: Thank you very much for your suggestion. Following your suggestion we have added Figure 7 at the end of the article. Figure 7 depicts the singlet and triplet states and the ground state positions. But we have not been able to observe the S2 state experimentally, so compare the position of the S2 state with the pyrazine molecule. The modified content on line 273-282(Page9, Line273-282).
Point 3: The pulse energy of 4.5 MJ is too much it seems its a typographical error it should be 4.5 mJ.
Response 3: We are sorry for that. We have modified this content. on line 89. (Page2, Line89)
Point 4: There are many spelling mistakes which should be corrected.
Response 4: Thank you very much for your suggestion.We are sorry for that. We checked and revised.
Point 5: All transitions happening in less than 100 fs should have an explanation that how they are determined since the pulse width is 100 fs and the cross-correlation between pump and probe is 200fs so any measurement below 200fs should be either extrapolated or determined through some modelling..
Response 5: Thank you very much for your suggestion. The cross-correlation function is 260 fs in this experiment, and there are no kinetic processes smaller than 200 fs in our experiments.
Point 6: A model depicting the singlet and triplet states along with ground state position should be provided.
Response 6: Thank you very much for your suggestion. Following your suggestion we have added Figure 7 at the end of the article. Figure 7 depicts the singlet and triplet states and the ground state positions. The modified content on line 273-282(Page9, Line273-282).
If you have any questions else or some other suggestions, please feel free to contact us. Thank you again.
All the best
Naipisai Wumaierjiang
Reviewer 2 Report
The manuscript is devoted to an experimental investigation of the decay dynamics of photoexcited 2-methylpyrazine. Although the topic is interesting, there are several issues which need to be addressed by the authors.
1) The introduction could be improved. Why the authors linger on benzene? If the "channel-three" effect is relevant for 2-methylpyrazine, it should be explained more clearly.
2) How it is formed the photoion? Upon absorption of one pump and two probe photons? This should be stated explicitly, preferably in the methods section. In this respect, a scheme of the energetics (possibly showing also where the Rydberg states are located) would be very helpful to the reader.
3) According to the authors, "The 400-nm probe photon could not reach any Rydberg state; thus, 2-methylpyrazine had to absorb two probe photons to resonate with the Rydberg state". This is quite confusing. Is this referred to a situation in which the molecule has not been excited by the pump?
4) In equation 7, the energy of the probe photon should NOT be multiplied by 2. Again, a scheme of the energetics would be very helpful.
5) The authors should try to give some explanation about the very different decay behavior after 260 nm excitation with respect to 244 nm excitation.
6) It is not clear why the TD-DFT calculations have been reported. In fact, these calculations are not used to characterize the electronic states. Moreover, their validity appears to be questionable: in fact, according to TD-DFT, the S2 state has a vanishingly low oscillator strength, while the authors claim to have excited the S2 state.
Author Response
Please see the attachment.
Author Response File: 
Author Response.pdf
Round 2
Reviewer 2 Report
Ok with author's modifications.
