Lichtgedanken 02

Editorial 45 02 | LICHT GEDANKEN »The ratio of two attoseconds to one second corresponds to that of one sec- ond to the age of the universe.« What Prof. Dr Adrian Pfeiffer describes with this image is a time span so short as to be scarcely imaginable: one attosecond is the billionth part of a billionth of a second. It almost goes without saying that experiments conducted in such a short timeframe are not always predic- table. Nevertheless – or perhaps becau- se of this very fact – the 37-year-old is expanding his research on attoseconds. He has recently received two presti- gious scholarships for his work: €40,000 from the Daimler and Benz Foundati- on and €100,000 from the Volkswagen Foundation. The latter supports dar- ing research ideas with an uncertain outcome through its funding initiative »Experiment!« – failure is an accepted result, he states, when explaining the reasons for obstacles. Modifications are part of the research process But who wants to contemplate failu- re when they have a new idea for re- search? »Every scientist in physics to- day is exploring frontiers whether in optics or solid-state physics. It’s always a matter of extremes: ever smaller, fas- ter, bigger. As long as it’s terra incog- nita. That’s what makes experimental physics so exciting,« Pfeiffer explains. And that also implies the possibility of failure, it’s important not to fear failu- re, he states. No experiment works the very first time, says the Junior Profes- sor for Attosecond Laser Physics from experience. But nobody interprets the modifying of an experiment as failure, he explains: »That is simply the process of research. It’s much more usual for it not to work than for it to work.« There can be three reasons for this in the natural sciences according to Pfeif- fer. Faulty materials or technology, hu- man error on all levels, from setting up to evaluating the experiment or sim- ply a research idea that doesn’t work. »Unfortunately, you never know the real reason. It’s easy to start doubting yourself.« Water off a duck’s back, that’s not his style: »In that regard, I’m no wi- ser now, and I’m still an optimist. And I can still get very angry when things don’t work.« From such phases, he can also clearly deduce where the term »ab- sent-minded professor« comes from. He is then so immersed in his own thoughts and preoccupied with the problem because he would like to find out where the sticking point lies in the experiment, he continues. Once he had a crazy idea, he says. It could have very quickly brought pow- erful new insights to the field of spec- troscopy. But the experiment simply refused to work, and sooner or later he gave up. The sketch of the idea is still in his desk, but it probably won’t ever leave his drawer again. »I still don’t know what the problem was. And that still peeves me.« The physicist likes to quote the A-Team TV series: »I love it when a plan comes together.« But in the end, the constant ups and downs cons- titute for him everyday working life in science. »Research is like a roller-coas- ter ride,« the attosecond expert opines. Adrian Pfeiffer has made his hobby his job. What keeps him going? Coffee in the morning. And the excitement and the striving to find something new. That could be compared to someone who has a model railway, he says: »It’s not always much fun setting everything up but you do it anyway because you want to see it running one of these days.« Pfeiffer, who comes from Baden-Würt- temberg, also likes to be adventurous in his free time. He enjoys skiing, clim- bing and sailing, but often he can’t find time for them. After his lab work and teaching assignments, he is more likely to be found in the bouldering centre in Jena or on his mountain-bike. Constant progress required His research into attoseconds to which the native of Tübingen has dedicated himself since starting his dissertation, took him initially to Zurich in 2007 and to the Lawrence Berkeley Natio- nal Laboratory in California for three years. He has been a Junior Professor in Jena since 2013. A normal career path in science, says Adrian Pfeiffer. Con- stant progress and mobility are a must. That fits well with what the passionate scientist has to say about experimental physics whenever somebody asks him a critical question about the deeper me- aning and benefit: »It’s the engine for development in general. Just take lasers in medicine or computer technology – if you’re in favour of progress, you can’t be against experimental physics.« And as far as the big picture is concerned, he naturally likes to stick with his daring research ideas. Pfeiffer’s latest project that the funding initiative »Experiment!« by the Volkswagen Foundation is supporting with €100,000, focu- ses on »subcycle precision non-linear spectroscopy« and, as he ex- plains, it requires a radical change in thinking. Specifically, he is in- vestigating how long a group of light pulses requires to travel from their point of origin, a material sample, until they strike a detector. The problem with the experiment lies in the inaccuracy of the measure- ment, as all the optics involved which the light pulses pass on their way to their target, bring with them certain surface characteristics. »Even with precision optics, you have to expect variances of around 60 nanometres. T H E B O L D E X P E R I M E N T 45 As at the speed of light, this shifts the time of the pulse by several hundred attoseconds, it is impossible to find out anything about the dynamics in the sample with attosecond precision,« the young physicist explains. Neverthe- less, he shows his ingenuity and still makes an attempt — by motorizing all the optics between the sample and the detector. By repeating the experiment multiple times, Pfeiffer assumes that the average determined in the time taken for the light pulses to strike reflects actual timing differences in different ma- terial samples. For example, he would like to find out how quickly electrons react to intense light in different materials such as thin glass or crystals.