Ahmed Zewail


Interview, December 1999

Interview with Professor Ahmed H. Zewail by Professor Sture Forsén, Lund University, and David Dishart, student, 12 December 1999.

Professor Zewail talks about how he started in the field of femtosecond spectroscopy; the future of chemistry (3:51); his current work (5:43); his thoughts concerning femtosecond methods for studies in the living cell (7:15); encouraging students in Egypt to study science (8:34); how it is important to find time for thinking (12:19); how the Nobel Prize has affected his life (13:29); and how the Internet makes us more specialized (14:44).

Interview transcript

Professor Zewail, let me first congratulate you to this year’s Nobel Prize in Chemistry for your pioneering work on femtosecond spectroscopy. Would you like to tell how you got started in this interesting field that you have developed?

Ahmed Zewail: Well, you know, Professor Forsén, you know everybody thinks some times that science is done as a master plan and that somebody like me came from Mars and figured out everything and so on, but that’s really not the way it worked. We started at Caltech asking very simple questions: how do we understand the molecule dynamics or the dynamics of molecules, emotions and so on, molecules but in a coherent fashion. These molecules, there are millions and billions of them in the sample that we want to study, and they are all at random. And there are no relationship among them and we would like to just order them somehow so they all can behave at the end as if they are a single molecule at rejectory.

So in the beginning we were trying to develop new laser techniques to see how these molecules, if we prepare them coherent then study them in a coherent fashion that then we can learn about the intrinsic processes such as how does the energy move in the molecules, how molecules changing their orientation and so on. So we did some of the analogues of the powerful nuclear magnetic resonance techniques which you are very familiar with and used coherent pulses and pulse sequences. But then around 1980 I was asking the question: can we do the same thing in a single isolated molecule, completely isolated from the rest of the world? The environment is not there. So the question of using then a combination of molecular beams and ultra fast lasers came to mind and we started to initiate this research area which I had no idea what’s involved in terms of molecule beams but we had my students and I had to get into this area. And fundamentally we’re thinking about if we now excite an isolated molecule, no collision no /- – -/, that if we excite certain vibration in the molecule how would the energy move into all the other modes in the molecule.

And that was really the beginning of femtochemistry science …

There are many theories and many ideas of how this, and the typical one it goes back to your Arrhenius, namely that the energy will go in a random way. But to the pleasant surprise of all of us is that the energy was not randomising on the short time scale. We found actually that the energy goes from this mode to another mode and comes back even though we have millions, we have a whole forest of modes in the molecule, but the molecule is behaving very selectively and coherently and the molecules are very complex that we were studying. And that was really the beginning of femtochemistry science, because it immediately indicated to us that if we can excite molecules and initiate this in molecules on a very short time scale prior to their vibration and rotational and scrambling of energy and everything we should be seeing a whole new world of ordered coherence in them and by -87 we made what the Nobel citation called ‘the breakthrough’. Namely that by so doing we’re able to see the motions of the real atoms inside the molecules and with atomic scale resolution of the dynamics.

Professor Zewail, the resolution at which one can study chemical reactions has been constantly decreasing over the past century. Do you think it will be possible, or is it even necessary to go further, right there in the future field of autochemistry?

Ahmed Zewail: This is a legitimate question actually, because I wrote something about this, but the Nobel citation, which was very well written, actually pointed out that this is hint of the, if you like, there is a Guinness time. The reason for that it’s fundamental. It is not that we have to keep shortening the time. It turns out all molecular and biological systems have speeds of the atoms move inside them, the fastest possible speeds are determined by their molecular vibrations and this speeds is about a kilometre per second. One thousand metre per second, which means that if you have femtosecond time resolution or 10 to the -15 or 10 -14 second you have a distance resolution of about a 10th of an Ångström. That means really that you are now frozen all the chemical or biological structures on that times kill you can’t do any better.

What I think the OCT or sub-femtosecond is going to be important and I suggested this in one review article would be to go into the motion of the electrons. So, who knows it may be that we will see one day how we can localise also the electron just like we did with the nuclei. But I think that will be beyond the realm of chemistry and biology, you will be now addressing issues in physics looking at semi conductors and high energy physics and so on. But that’s … I don’t want to commit myself and then proven to be wrong later but that’s basically what I think about it at this point.

How do you see fusion directions in the studies of chemical and biological phenomena or time is loosen or the aura of femtoseconds, would it be possible to make sort of a snap shots x-ray the fraction in femtoseconds time scales or electron defraction. How do you see the future let’s say the next 10, 15, 20 years?

Ahmed Zewail: I’m glad you asked this question, Professor Forsén, firstly because I thought in my Nobel Lecture I pointed that I was delighted that the Swedish Academy of Science did not quote anything about my current work right now, because the current work that my group is focusing on is actually both the time resolve electrons and possibly x-rays to be able to get the architecture of these molecules, the molecular structures themselves, of very complex biological systems. That’s the ultimate goal. We have succeeded so far to do this defraction type experiment on smaller molecules and look at intermediate transit structure but you can imagine the power of this maybe in 10 years, when we are able to look say at the intermediates of proteins process. Or the motions of some of the DNA structures that we are interested in. The effect of salvation does the hydrophobic forces play a fundamental role in the process of folding. There was just a numerous questions I would like to ask and we really have to look at these snap shots at early times.

Femtochemistry provides really strong possibilities for new drugs, do you think it will ever be possible to study at that level in a living cell, perhaps study enzyme reactions?

Ahmed Zewail: Well. that will be really a fantastic advance. Of course the difficulty usually we get into this at this point in time is that in the cell there are the medium itself and the water and so on but one advantage of the femtosecond time resolution, and we demonstrated this in a number of studies, is that even in liquid type environment same coherence I was talking about and the motions that we see we can actually isolate because the protonation from the solvent is not turned on yet on that timescale. So, some people have started to use actually femtosecond methods to image processes in cells. There has been work on DNA, in fact I’m involved in this with my colleagues at Caltech in the looking at the transport of electrons in DNA. A lot of work has been done on proteins including cytocromoxides and others so, you’ll see a variety of applications in the coming years.

I know that you have been or you have a strong desire to promote science and help young scientist’s in your country of birth, Egypt. What are your plans in this direction? Could you tell something about that?

Human resources are just tremendous in Egypt but we need the science base …

Ahmed Zewail: Yes, I do feel quite strongly about this that probably one of the things that unfortunately this age now to get a Nobel Prize is to really use part of it to help the young people get excited about science. In the States, in the world at large but also with particular focus on Egypt because I came from Egypt and I owe Egypt a lot to what I am now. And I do feel that there are tremendous amount of talent in Egypt, human resources. Human resources are just tremendous in Egypt but we need the science base, we need the correct science base. How to get these people to interact with each other. When I give a lecture on Egypt there are thousands of people in the lecture hall, so obviously they would like to go to science and they would love to do science, but you really have to get the correct science base in order for them to interact, so we are hoping to have maybe a little Caltech maybe a little /- – -/ do you know that just to start something there that really both Egyptians and colleagues from the western world and so on can interact with each other, give the students the exchange and do science at the frontiers.

I think the Nobel Prize will help you in this respect?

Ahmed Zewail: I think the Nobel Prize helps for a number of reasons. Number one, if I can be frank, there is these people will feel by getting a Nobel Prize that I’m one of them, that it is possible to contribute on the world map of science and technology. That’s not only in the hands of the Swedes and the Americans and the British and so on. That they could if they worked hard and they have the abilities and so on, they can achieve even on the highest level. And the other thing also which I’m hoping for is that the government in Egypt is willing and interested in promoting science and technology and this is an ideal time now to be able to do something.

Are there certain fields of science which you think might be especially well suited to young scientist in Egypt?

Ahmed Zewail: I think in Egypt and all over the world you know, David, there are many books I read talking about the end of science. There are many, many books I’ve read and I think this is quite naïve actually because we all just try to uncover something. But the universe at large is full of questions that we still don’t know anything about and there will be always young people brilliant who are going to make new discoveries. I mean if you think in 1999, now this is an ending year of this millennium and you just think about the world of the very small, thinking about manipulating the atoms and the molecules. Think about the whole world of biological complex sciences. We still don’t understand the way a protein folds the way it does. I mean it’s an amazing thing. So, all of this is opened up, you go to the very big, you go to astronomy, we still don’t understand how the big bang and evolving all the way to the human species and so on. So all of this is going to be a very, very exciting to the new people. But for me to sit down here, even as a Nobel Laureate and make a prediction about which science I think that will be a mistake.

Scientists are supposed to be creative and surely they certainly are and you were a most creative man. What are your best creative moments, is it in the shower when you are listening to music in the early mornings can you say something about that?

Ahmed Zewail: Yes, it’s a crazy actually moments you just never know. Well, one of the things I enjoy most is to be left alone with a book. I am not one of the new media experts working all the time with my computers and the PowerPoint’s and things of that sort. So, I’m an old fashioned still in this regard but these are the moment where I really can be creative, if I am, to be left alone with just a book and piece of paper and to be thinking. And I think actually one of the messages to the young people building on David’s question, is the internet and all this wonderful thing we have, these are not thinking machines. These are information gathering, but you should have some time to think and that’s very important.

Nobel Laureates usually complain that getting the Nobel Prize perturbs their life infinitely and how do you try to get away from, to find your sort of precious moments or creativity in the future?

… then he made a very famous statement, something to the effect that this is the last 20 minutes of peace of your life. And he was right …

Ahmed Zewail: Well, I’ll tell you a story and I’ll tell you how I’m trying to do it. When they called me with the Nobel call from Secretary General of the Swedish Academy it was twenty minutes to six and he said well that was well hope I’m not disturbing you but I am the Secretary General of the Swedish Academy. Of course you can imagine I was frozen in time when he said that but then he made a very famous statement, something to the effect that this is the last 20 minutes of peace of your life. And he was right at six o’clock exactly until today I just have not had the time to be in equilibrium with myself. We receive thousands of e-mails and faxes and so on. But I want to really focus on doing this two things I really would like to focus on science and the excitement of science and to help with science. So, that’s my intention to focus my efforts there and I hope I will be able to do so.

Back to your previous answer going to the internet, there’s a lot of talk about information overload that there’s so much information flowing out especially with computers and things that people get sort of too much and can’t think any longer. Do you think that that could be a problem for scientists that it could eventually even become detrimental that there so much information that it becomes difficult to sort of concentrate on a specific area?

Ahmed Zewail: Yes, I do have a concern however, humanity has a great way of adapting and I’m sure scientists of the future, probably after I leave this planet, earth will have a new way of dealing with the internet but I do have a concern in the transition period, namely that … I’ll give you an example, when I was a graduate student and we get a journal, let’s say in your case molecular biology or if you’re not chemical physics or something. You know we are dying to take the whole journal and find out the different areas of science. Professor Forsén is aware of many areas that going on in from physical chemistry to molecular biology but because of the internet nowadays people are getting more and more specialised and so you found that I found with my students they don’t necessarily look at journals any more, but they print right away from the internet what’s relevant to what’s he doing you see. Yes and you’re probably a living example.

I’m guilty I’ll say.

Ahmed Zewail: So there is a danger one has to really be knowing much more because you can’t be too narrow on science.

We have actually received a question from Egypt from a student at the American University in Cairo and he says Sir, addressing you, in your judgment, who was the best chemist, physicist, biologist in this millennium?

Ahmed Zewail: Millennium, yes, not century, well I think that’s a million dollar type question. But I would like to tell this young person who’s asking the question from the American University in Cairo, is that in science doesn’t work this way. Scientists contribute in a variety of ways and I don’t think I can singular one even including Einstein, that I can say that he’s the best. We don’t work like the best basketball player and the best musician and so on. Science is a collective effort. I built on the efforts of a previous scientist, others will build on the work I’m doing and if I look at the whole scope from chemistry to biology to physics, it’s just the list is too long to mention just one and it’s not fair to the others.

I see that our time is drawing to a close here, your 30 minutes and I would like to thank you very much Professor Zewail for coming in and letting us interview you in these nice conditions. Thank you very much.

Ahmed Zewail: Thank you so much.

Did you find any typos in this text? We would appreciate your assistance in identifying any errors and to let us know. Thank you for taking the time to report the errors by sending us an e-mail.

To cite this section
MLA style: Ahmed Zewail – Interview. NobelPrize.org. Nobel Prize Outreach AB 2023. Sun. 1 Oct 2023. <https://www.nobelprize.org/prizes/chemistry/1999/zewail/interview/>

Back to top Back To Top Takes users back to the top of the page

Watch the 2023 Nobel Prize announcements

Don't miss the Nobel Prize announcements 2-9 October!

Watch the live stream of the announcements.

Explore prizes and laureates

Look for popular awards and laureates in different fields, and discover the history of the Nobel Prize.