The demonstration of a 53-attosecond x-ray flash by a research team from the University of Central Florida (UCF) is the fastest light pulse recorded to date, and beats the team’s own record of a 67-attosecond extreme UV light pulse, set in 2012. University of Central Florida Professor Zenghu Chang broke the record for the fastest light pulse. Courtesy of University of Central Florida. Soft x-ray pulse duration of 53 attoseconds and single pulse streaking reaching the carbon K-absorption edge (284 electronvolt, or eV) were achieved by utilizing intense two-cycle driving pulses near 1.8-μm center wavelength. With the shortest pulse duration decreased by 20 percent, the spectral range (100 to 330 eV) where the high harmonic pulses were characterized in the time domain was doubled. The UCF team also determined experimentally and quantitatively that the attosecond pulse duration was limited by the chirp instead of the bandwidth in the new spectral region. The pulses were shorter in wavelength as well as duration. The 53-attosecond light pulse reached the so called “water window,” where carbon atoms absorb strongly but water does not. The x-ray source demonstrated in this work could make it possible to observe charge migration by exploiting transition from the carbon core level to the unoccupied valence orbitals at the carbon K-edge with attosecond resolution. Such attosecond sources — synchronized with few-cycle IR fields or high-energy XUV pulses — could bring opportunities to study biological or chemical science and strong-field physics. “Such attosecond soft x-rays could be used to shoot slow-motion video of electrons and atoms of biological molecules in living cells to, for instance, improve the efficiency of solar panels by better understanding how photosynthesis works,” said professor Zenghu Chang. An attosecond is one-quintillionth of a second. In 53 attoseconds, light travels less than one-thousandth of the diameter of a human hair. The research was published in Nature (doi: 10.1038/s41467-017-00321-0).