00:10
Hello, and welcome again to 英語でサイエンスしナイト. This is Asami, and you're listening to Part II of the podcast episode series for 六月の科学系ポッドキャストの合同企画 hosted by 庁内細菌相談室の鈴木大輔さんがオーガナイズしてくれています。
観察というテーマでお送りしています Part IIです。 And I know at the end of Part I, I said that I'm going to talk about the spatial resolution story, which is the other sort of axes of, you know, things we're interested in, in ultrafast molecular dynamics.
But I decided that it's going to be too hard for me to condense into sort of entertaining chunks of stories without getting too, too, too technical and also without getting into like two hour podcasts.
So I am just going to ditch that topic. Sorry about that. But if you are dying to hear, you know, the spatial resolution story, because it's truly an amazing scientific and engineering feat of the recent technologies, and it's really fascinating and amazing that we can do this type of experiments at all.
But yeah, if you really want to hear it, you know, our DMs are always open, so slide in. Anywho, for this episode, I wanted to introduce just one more observation technique that people in my field use, which is called pump probe experiment.
If you've listened to the previous episode, we know that from the past 50 plus years or so, we have come so far in being able to have ultrafast lasers that produce super intense, super short time pulses that comes out in extremely precise and regular intervals. So extremely precise clock, right?
And with that tool, we are now able to add time axes to the existing observation techniques in the chemical reaction. So backtrack from this, you know, a little bit. For the good part of modern chemistry history, scientists have been mostly concerned with the questions of what is the starting materials you need in order to get the final products you want, right?
So like what chemical mixtures do I need to start with in order to get to the final desired material, like whether that final desired material is something that cures cancer or removes your headache or morning sickness, what have you.
03:07
And naturally, the technique that was developed to answer this kind of question, right, was a characterization technique. And nowadays we can routinely detect single molecule level resolution, which is really amazing.
And you see this sort of in fictionalized action in TV shows like Bones or CSI Miami or Aura, where they're able to extract critical molecular signature, like the tiny amount of molecular signature in a huge sea of background noise. Really impressive.
And, you know, if you're a chemist, you would know, but the tools that are commonly used are things like mass spectrometry, UV-Vis or IR or Raman spectroscopy, NMR, things like that, in order to determine, you know, what the final product is and do sort of like a kotaeawase of what you synthesize or what you found in a sample.
But in the early 20th century, people start to wonder about how the chemical reaction takes place. So not just like what do we end up with, but how does it go from chemical A to B?
In order to answer that question, though, we needed a new tool. And, but for the first half of the 20th century, we just simply didn't have that tool, right? Instruments weren't as precise or had this temporal resolution that we needed.
And the error was too large to say anything conclusive about the process of chemical reaction. So it was, you know, not designed to be able to observe things that happen in real time chemical reaction resolution.
So in comes the ultrafast laser that we talked about in a previous episode. Now we have a super precise way to observe the chemical reaction. And at the beginning of this podcast, I mentioned palm probe technique. You can think of this as a start and stop technique.
But essentially, we need two pulses to do this experiment, right? The first pulse is the starter pulse. This initiates the chemical reaction, injecting energy in a form of photons to the system. So you start the reaction. That's the first pulse.
The second pulse comes later, let's say 10 femtoseconds later, to stop the reaction. But really, this isn't stopping the chemical reaction. I'm using, you know, air quotes here. Because it's more like a camera. It captures what the molecule looks like 10 femtoseconds after the reaction started.
And now we repeat this process, palm probe, palm probe, but this time, you probe at a different timing. So not 10 femtoseconds later, but 10 plus 10 femtoseconds later, and then 10 plus 10 plus 10 femtoseconds later, and so on and so forth.
06:14
And by the way, this interval doesn't have to be, you know, regular, it can be anything you like. But at the end of the day, we basically end up with snapshots of molecules at different time delays after the chemical reaction began.
And now we can make something like a para para manga of molecules. The more snapshots per second you have, the smoother your para para manga movement looks like, which is why we want ultra short pulses to capture the molecular dynamics with the best time resolution possible.
So really, you can say that people who are in the business of ultra fast molecular dynamics are mangaka, right? Is that too much of a stretch? I don't know. Anyway, this is pretty simple in concept.
But this is a very difficult experiment. Just imagine though, you know, having to have two laser pulses overlap in space and in time, right? And imagine if the time domain that you're trying to overlap is, you know, let's say 100 femtoseconds pulse duration.
That means 100 femtoseconds pulse traveling at the speed of light equals to about 30 nanoseconds. Like, good luck trying to overlap two things over 30 nanoseconds, sorry, nanometers range, really.
So these are really not that easy of an experiment, but a very simple and effective way to add time axes to your existing observation techniques.
So now you can add the time, which means you can observe the change in molecular structure over some time. And that gives us information like time constant of lifetime of specific states, or how which part of the molecule moves in order to become a different molecule at the end.
Yeah, whatnot. And, you know, we talked about here as pump probe using two laser pulses, but it doesn't have to be two laser pulses. You can do probe pulse, so the second pulse, right, the capturing pulse, that can be done in, for instance, electron pulse.
So instead of having a bunch of photons, you have just a bunch of electrons in the packet, or x-ray, so like very, very high energy photons, and that gives you a different information.
09:05
So really, this is extremely versatile technique that is pretty difficult to implement, but worth implementing if your question is about what happens during the chemical reaction.
So, again, another sort of information packed episode, but I hope you enjoyed this. It's really interesting to think about observation, you know, things we as scientists do every day, but don't think about or give a lot of time thinking about it.
And I just wanted to end this episode with a couple of notes, meaning observation just isn't limited to experimental observations, right? I think observation is the skill that especially scientific education gives a good training on.
Because many times, you need to be able to observe your surroundings, your experimental setup in order to troubleshoot your senpai in order to learn skills and protocols, and how they think, and how they approach troubleshooting.
And you just learn a lot by being a good observer. And I think scientists get sort of a hardcore training on that. And not just that, right? When you have raw data, oftentimes, raw data alone, it doesn't make any sense.
And you need to have good eyes, be a good observer, in order to see some little signals in the sea of background, or in order to tease out the information that you specifically want, and be able to say that this is indeed the signal you're after.
You also need to be a good observer in order to even pick a research topic, right? Because you want to sort of look at what other people are doing and fill in the gaps of what they haven't done or what they have overlooked. And that's another observation skills that you really need.
Yeah, it's just being aware of your surroundings, trying to critically engage what's around you. That's definitely an underrated skill that science education, I think, gives a lot of opportunities to during this formative years as a scientist.
So, you know, once again, everybody should do science. But um, yeah, I guess I don't really know where to where I'm going with this. But thank you again, Suzuki-san for providing this topic. I had lots of fun thinking about what to talk about and sort of share with listeners what I think of observation as.
12:11
So and thanks for listening. And do give a listen to other podcasts. I think we have about 13 or 14 different podcasto bangumi who are participating for this month's godo kikaku. So give a listen. I'll also go listen to hopefully everyone's episode. And let us know, we love getting feedback. So let us know in tweet or DM or other forums, what you think about it. Thanks.
That's it for the show today. Thanks for listening and find us at Eigo de Science on Twitter. That is E I G O D E S C I E N C E. See you next time.
