I work in Heinz Burtscher's group at the University of
Applied Sciences in Windisch (Fachhochschule Nordwestschweiz) in Switzerland as a research scientist. We invent and build instruments
for aerosol measurements. Some of the nicest things that have come out of our group are the miniature diffusion size classifier, a handheld
instrument to measure ultrafine particles, which I developed together with Peter Steigmeier and Corey Houle, the partector, an
aerosol dosimeter, developed by my master student Dominik Meier, and its extension, a handheld TEM sampler for nanoparticles.
I wrote Mie scattering code for LabView in February 2004, and updated it in August 2005 to output everything the original Bohren and Huffman code provides. The new version also allows you to specify the angular resolution of the output. If you use LabView and do light scattering experiments, you might find this useful. Download my LabView Mie scattering demo program! The VI uses a dll file which is basically Flatau's C translation of Bohren and Huffmans Fortran Mie scattering code.
I wrote LabView code to solve the NNLS problem, that is, to solve the least-squares problem Ax=b with x being constrained to positive numbers. The basic algorithm was invented by C.L.Lawson and R.J.Hanson and is published in Solving Least Squares Problems, Prentice-Hall 1974, chapter 23. I just adapted it to the G programming language. Download LA_NNLSfit.zip (103KB).
During most of my school days, I was sure I would go on to study maths later on - but this changed in the Gymnasium (high school), where I had a horrible maths teacher in the first half year. Luckily, he retired, and for the following four years we had a better teacher - but the damage had been done! In physics, however, I had a (for me!) great teacher in the form of Aegidius Plüss, who was certainly the prime inspiration for me to study physics. I started studying physics at the ETH Zürich in 1991 and received my diploma in experimental physics in autumn 1996, specializing in nonlinear optics. My diploma thesis was on photorefractive effects and photoconduction in DAST, which is an organic nonlinear optical crystal. I wrote my diploma thesis in the group of professor Peter Günter. Of course, as a diploma student you have nothing to do with the professor at all. My motivation for this topic came from two interesting lectures on nonlinear optics by Christian Bosshard, who is now at CSEM, the Swiss center for electronics and microtechnology in Alpnach. Christian, and in particular his Ph.D. student Stéphane Follonier were the supervisors for my diploma thesis. Christian is now head of a section at CSEM in Aplnach, while Stéphane, originally from a Swiss mountain valley (The Valais), is now head of the CSEM division in Landquart, in another Swiss mountain valley.
I studied together with
and Richard Hahnloser, who are
now professors in Vancouver and at ETH Zürich; and with
Jörg Rychen and
Gabriel Spühler, who are now running their own high-tech companies.
In 1997, I started working on my Ph. D. thesis in the group of professor Hans-Christoph Siegmann. I had been lucky during my
exams on general experimental physics for the second intermediate exam at ETH (2. Vordiplom), and received very high marks.
HC, as we called him, who taught the class, remembered this, and offered me a position as Ph.D. student in his group.
I was one of HC's last Ph.D. students - he was forced to retire at the age of 65 in 2001, and moved to Stanford, where he remained
a very active physicist until his untimely death in 2009 (visit his webpage for an overview
of his life as a physicist).
HC invented the spin-polarized electron source, and was generally a very creative person.
Unfortunately, I again had little to do with the professor himself, because I decided to try to measure the electronic relaxation
time in metallic nanoparticles, something which I started to do in the surface science group of professor Martin Aeschlimann,
who at that time was still at ETH as a researcher (Oberassistent). Aeschli (as we called him) then got a job as assistant professor
(C3) in Essen, Germany, and I also went there during a part of 1998 - shudder! Aeschli has since moved on to the university
of Kaiserslautern as a full professor and continues to investigate ultrafast phenomena in his
ultrafast surface science group.
My thesis project was to determine the relaxation time of "hot" electrons in nanoparticles. This relaxation time
is of the order of a few femtoseconds - that's not very much! I used a frequency-doubled ultrafast Ti:Sa Laser with a pump-probe setup
to measure those short times. I showed that it is possible in principle to determine the relaxation time in
nanoparticles. I was also able to see differences between different metals (Silver, Gold, Palladium), however,
there seems to be no size dependence of the relaxation time due to electron-electron scattering in particles from 100nm in diameter
down to 5 nm diameter - that's already pretty small, these particles consist of only 4000 atoms. At the end of 2000,
I finished my graduate studies at ETH Zürich with a PhD thesis entitled 'ultrafast electron dynamics in gas-suspended
nanoparticles'. It's available online, but
I doubt it's worth the read...
After completing my PhD, I had an offer to go to Berlin which I turned down, in part because of my previous Germany-experience in Essen, but mostly because I wanted to go to Hawaii - I applied for funding to do a postdoc there. In the meantime, I worked on the development of an electrical diffusion battery at the university of applied sciences in Windisch for about half a year and, when my funding application was granted, I went to Klaus Sattler's nanoscience lab in beautiful Hawai'i for a year. I returned to Switzerland toward the end of 2002 and went back to Windisch. Not exactly the right choice for a distinguished career in science; but when I looked at the price to pay for a real academic career, I knew it was nothing for me.
This page wouldn't be complete without a reference to my grandfather, Markus Fierz, a theoretical physicist. I can't really remember, but I suppose that he must have influenced my decision to study physics in some way. His father, Hans-Eduard Fierz, was a professor for chemistry at ETH. I didn't know my great-grandfather of course (he died in 1953 at the age of 71, shortly after retirement - from a type of cancer that is triggered by the kind of chemicals that he must have been using during his career), but I recently found a nice picture of him with an assistant in the lecture hall, my great-grandfather is to the left: