Synopsis

Molecular snapshots with femtosecond x rays

Physics 3, s88
Early results from the Linac Coherent Light Source expose the inner dynamics of molecules during ionization with ultrashort x-ray pulses.
Illustration: Courtesy of the LCLS

Imaging the internal dynamics of excited atoms and molecules with high spatial resolution requires fast, energetic pulses of x rays. As Matthias Hoener and colleagues from an international collaboration report in Physical Review Letters, initial results on how molecules absorb high-energy, femtosecond x-ray pulses are now emerging from the Linac Coherent Light Source (LCLS), which began operation last year at SLAC National Accelerator Laboratory in California, US.

Hoener et al. used the LCLS free-electron laser to produce x-ray pulses with wavelength 1.1nm ( 1100eV photon energy) and pulse widths from 280 femtoseconds down to 4 femtoseconds. The team directed the pulses at puffs of nitrogen ( N2) gas and analyzed the resulting ionized molecules with a time-of-flight mass spectrometer.

All the x-ray pulses delivered the same total amount of energy to the nitrogen gas, but Hoener et al. observed that the spectrum of ions depended on the pulse width: Long duration pulses completely stripped the electrons from the nitrogen atoms, but shorter pulses were not able to produce the fully ionized state. Hoener et al. argue that for shorter pulses, the cycle of an outer-shell electron falling into the emptied core-shell (Auger decay) cannot occur quickly enough, limiting the achievable ionization.

The experiments reveal the fundamental dynamics of how molecules absorb high-intensity, hard x rays and bear directly on what may be possible in future single-shot studies of chemical structure and dynamics—one of the most important applications of free-electron lasers. – David Voss


Subject Areas

Atomic and Molecular PhysicsOptics

Related Articles

Midcircuit Operations in Atomic Arrays
Atomic and Molecular Physics

Midcircuit Operations in Atomic Arrays

Three research groups have exploited the nuclear spins of ytterbium-171 to manipulate qubits before they are read out—an approach that could lead to efficient error-correction schemes for trapped-atom computing platforms. Read More »

Photonic Picture of High Harmonics
Quantum Physics

Photonic Picture of High Harmonics

A new interpretation of high-harmonic generation—the cornerstone of attosecond physics—paves the way for quantum applications of this process. Read More »

It’s a Trap—for Lanthanides
Atomic and Molecular Physics

It’s a Trap—for Lanthanides

Trapping and imaging single dysprosium atoms extends the utility of optical tweezer arrays to electronically complex species, opening the door to new quantum physics studies. Read More »

More Articles