Photoelectron diffraction from laser-aligned molecules with X-ray free-electron laser pulses

Abstract

We report on the measurement of deep inner-shell 2p X-ray photoelectron diffraction (XPD) patterns from laser-aligned I2 molecules using X-ray free-electron laser (XFEL) pulses. The XPD patterns of the I2 molecules, aligned parallel to the polarization vector of the XFEL, were well matched with our theoretical calculations. Further, we propose a criterion for applying our molecular-structure-determination methodology to the experimental XPD data. In turn, we have demonstrated that this approach is a significant step toward the time-resolved imaging of molecular structures.

Structure determination of molecules in an alignment laser field by femtosecond photoelectron diffraction using an X-ray free-electron laser

“…A pulsed supersonic molecular beam of sample I 2 was introduced into the interaction region between facing velocity-map imaging spectrometers (VMIs) and was intersected by collinear pulsed lasers (Nd:YAG laser and XFEL)14 (see Fig. 1).…”

“…In this Article, we report on the profile of I 2 p photoelectron diffraction from I 2 molecules with a higher degree of alignment compared with our previous work14, which was obtained using XFEL pulses from SACLA. Owing to the better alignment, we have succeeded in determining the average internuclear distance for the I 2 molecular ensemble in alignment Nd:YAG laser fields by applying our molecular structure determination methodology9 to the newly observed I 2 p photoelectron diffraction profile.…”

“…Therefore, the UXPD method extends the time-dependent structure investigations of the UXD method to new classes of samples that are not accessible by any other method, e.g., dilute samples in the gas phase such as aligned, oriented, or conformer-selected molecules. To utilize this capability, several proposals8910 and test experiments11121314 on the UXPD methods have been published. However, results on the transient structure of molecules during chemical reaction, which will be obtainable with the UXPD methods, have not yet been reported.…”

“…In the pioneering works on the UXPD method, sample molecules (C 8 H 5 F1113, C 6 H 4 Br 2 1213, and I 2 14) were adiabatically aligned by the electric fields of Nd:YAG lasers. The reported diffraction profiles for such molecules can be regarded as a snapshot of a “molecular movie” visualizing the femtosecond structural dynamics in a pump-probe experiment.…”

Probing and extracting the structure of vibratingSF6molecules with inner-shell photoelectrons

“…[23], multiple scattering theory was used to fit to experimental photoelectron diffraction images to extract bond lengths and bond angles for small oriented molecules. It has been shown that the method can be extended to laser-aligned molecules [30,31]. In Ref.…”