Two-colour X-ray pulses record the same sample at two moments in time.
One big dream of ultrafast science has been to watch changes in nanoparticles or biomolecules on their natural timescale. Experimentally, this can be realized by taking two snapshots of the same nanoscale object only femtoseconds (millionth of a billionth of a second) apart. A new capability of the European XFEL has recently enabled a big step towards the realization of this dream: the X-ray laser can produce subsequent flashes of two different colours, that are bright enough to image a particle twice within femtoseconds. However, a big challenge remained: no detector is fast enough to record the two snapshots separately—they end up on top of each other in a single image, comparable to a double-exposure photograph. Scientists now successfully employed two complementary methods to disentangle two diffraction patterns captured by the same X-ray detector. The results by an international team of researchers have been published their results in two separate articles in Nature Communications.
While both take advantage of the different colours or photon energies, one method exploits the capability of the detector to discern energy levels for each individual pixel, while the other uses mathematical reconstructions. Its inventors call the latter method Dichography. One of the leading scientists compares the technique to an extreme high-speed camera: “To my knowledge, these are the fastest nanoscale movies ever recorded, if by movie we mean multiple frames of the same object,” says Alessandro Colombo from the Department of Physics at ETH Zurich in Switzerland.
Read more on the European XFEL website
Image: A double exposure image can picture the same subject at different points in time. Disentangling the two events can be challenging. However, in this famous photograph, it can be assumed that inventor Nikola Tesla was not in the room when the electric discharge occurred.
Credit: Dickenson V. Alley. License: CC-BY-SA