?

Log in

No account? Create an account
Sauntering Vaguely Downward [entries|archive|friends|userinfo]
Mad Scientess Jane Expat

Serious Business | Flickr
Bounty Information | Wanted Dead or Alive: Mad Scientess Nanila
Deeds of Derring-Do | Full of Wild Inaccuracies and Exaggerations

Why Yes, I Am Awesome [20100429|11:16]
Mad Scientess Jane Expat
[Tags|, , ]

[personal profile] miss_haitch challenged us to cast off the shackles of forced humility and expound upon one reason why we are awesome. I choose to talk about something I've barely mentioned in this journal since I defended my thesis in September 2002: my PhD in experimental physical chemistry.

I obtained my doctorate after five years of intensive study in what is generally recognized as one of the most difficult types of experiment to perform in any scientific field: coincidence spectroscopy. The experiments are difficult to set up, difficult to run and most of all, difficult to interpret. It's only now that I have some distance from having performed them that I recognize just how tough my doctoral work was.

I'll try to break down a coincidence experiment into comprehensible steps.

  1. Choose a chemical that is formed temporarily during a reaction. These are called "transition states" or "transient species". You can choose a system with very simple atoms, which will make the theoreticians happy because they can generate a complete dynamical model of the reaction. Alternatively, choose a system that has some important implications for atmospheric chemistry, such as clusters of NO2 molecules, or combustion chemistry, such as oxygenated radicals formed when hydrocarbon fuels are burned.

  2. Find a way to stabilize that chemical. This is not easy. There are many transient species formed during reactions, and they only live for a matter of microseconds, or sometimes nano- or picoseconds. That's really not long enough to make a measurement of its properties. The method I used for my PhD research was to create a negative ion of the chemical. Of course, we didn't always know if this was going to work in advance, so sometimes a few different combinations of precursor chemicals would have to be used.

    Once you have a reliable source of the chemical that can be made into a molecular beam, you can proceed to the next step.

  3. Measure the chemical's properties by dissociating it in a controlled fashion. This means using a laser. Your laser should be at a wavelength that's appropriate for the kind of environment that your chemical will experience during a reaction. For atmospheric reactions, this generally means somewhere in the visible or near-ultraviolet. You want to pulse your laser so that it intersects the chemical beam periodically. Then you must measure all of the products of the chemical simultaneously. You want to know the masses and the velocities of the products so that you can completely reconstruct where the energy from the laser went into the chemical. You need sophisticated detectors for this measurement. Because you don't want to count more than one event per laser pulse and you want a statistically significant number of events, it often takes days of continuous running to get enough data to analyse a given chemical. Since the experiment is large and complicated, with lots of bits that are prone to drift and require frequent adjustment, this takes a long time. If you've been patiently tending an experiment on a particular chemical for four days, going home only to shower and eat, and suddenly there's a power outage or your data acquisition computer crashes, it is very tempting to go temporarily insane and smash things. With fists, not lasers.

  4. Determine the chemical's properties using computational analysis. Once you've finally gotten all of this to work, you must now interpret the results. You have to try to figure out how the energy from the laser pulse was distributed in the chemical. Where was the electron that was knocked off of the chemical, and how much energy did it take away? Which bonds did the laser pulse affect and cause to vibrate? Can you see any rotation taking place? If you are comparing several types of similar chemicals, like alcohol derivatives, why did some of them dissociate and others not? Finding answers to these questions can sometimes be aided by performing what are called ab initio ("from first principles") calculations on the chemical. Then you can use the bond lengths, angles and molecular orbitals to create simulated spectra to compare to the experimental ones.

  5. Marshal this information into some sort of order; attempt to publish. The fun isn't over yet. Just because you understand your results doesn't mean that anyone else will. And with experiments this complex, simplifying the explanation is nontrivial.


Even though it's been nearly eight years since I ran a coincidence experiment, I know I could go back into my old lab and run it now. It's that ingrained in my memory. In fact, I think I could do it even better than I did before, as I've picked up a much clearer understanding of signal processing and analysis from the work I've done since I left physical chemistry. And I think that's pretty awesome.

Now I think you should tell me why you're awesome.
linkReply

Comments:
(Deleted comment)
[User Picture]From: nanila
2010-05-06 17:48 (UTC)
It's funny to think about that now. I remember being genuinely disappointed that I didn't get it before I was 25, because that was my original goal. I believe I justified this to myself because I was certain I'd be dead by the time I was 40.
(Reply) (Parent) (Thread)
(Deleted comment)
[User Picture]From: nanila
2010-05-06 17:49 (UTC)
Ossom! (Also, a little bit crazy. But I think that is okay.)
(Reply) (Parent) (Thread)
[User Picture]From: victorine
2010-04-29 17:37 (UTC)
I think I'm awesome because I have two jobs, a husband, a cat, and I haven't killed even one person yet! In all seriousness, I think I am an awesome massage therapist. I have moments when I doubt my skills, but when people get off my table they always feel better. Some have even told me that whatever body part was jacked up is now fixed. (maybe I'm too awesome ;p)
(Reply) (Thread)
[User Picture]From: nanila
2010-05-06 17:50 (UTC)
That's pretty awesome, G! I still remember you giving me a treatment once - it was incredibly relaxing. I don't think it's possible to be too awesome at giving massages.
(Reply) (Parent) (Thread)
[User Picture]From: sneakypeteiii
2010-04-30 05:09 (UTC)
I defended my PhD after 5.3 years of grad school, though I couldn't actually decide what field to be in. I published in chemical physics/dynamics and in stable isotope geochemistry, but now I'm apparently in chemical oceanography and/or ecology.

I built my kitchen during grad school year one with MY BARE HANDS, a circular saw, and screw gun. Bless you, Ikea. Some other guys did the counters and sink. This is partially why I haven't yet moved to Seattle.

I am a semi-professional guitarist. For instance, I've had the distinct shame of playing a guitar solo to follow Flea's solo on stage, and last weekend I flew up to San Francisco for 24 hours just to record tracks for a friend's album.
(Reply) (Thread)
[User Picture]From: nanila
2010-05-06 17:52 (UTC)
You are totally awesome. I admire your kitchen construction. I didn't know you were a musician. This makes you even more awesome, and is also rather sexy.
(Reply) (Parent) (Thread)