Abstract
We have successfully determined the internuclear distance of I2 molecules in an alignment laser field by applying our molecular structure determination methodology to an I 2p X-ray photoelectron diffraction profile observed with femtosecond X-ray free electron laser pulses. Using this methodology, we have found that the internuclear distance of the sample I2 molecules in an alignment Nd:YAG laser field of 6 × 1011 W/cm2 is elongated by from 0.18 to 0.30 Å “in average” relatively to the equilibrium internuclear distance of 2.666 Å. Thus, the present experiment constitutes a critical step towards the goal of femtosecond imaging of chemical reactions and opens a new direction for the study of ultrafast chemical reaction in the gas phase.
Highlights
We have applied the ultrafast X-ray photoelectron diffraction (UXPD) method to a simple I2 molecule to determine its structure ‒in other words, its internuclear distance ‒in the alignment-laser field. In this Article, we report on the profile of I 2p photoelectron diffraction from I2 molecules with a higher degree of alignment compared with our previous work[14], which was obtained using X-ray free-electron lasers (XFELs) pulses from SPring-8 Ångström Compact free-electron LAser (SACLA)
A pulsed supersonic molecular beam of sample I2 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]
Electrons produced by the XFEL pulses were accelerated towards the one VMI, which was operating in a velocity focusing mode, and detected by a microchannel plate (MCP) detector backed by a phosphor screen
Summary
A fundamental question arises: whether the structure of a molecule in an intense alignment-laser field is the same as that in its ground state or not To answer this question, we have applied the UXPD method to a simple I2 molecule to determine its structure ‒in other words, its internuclear distance ‒in the alignment-laser field. We have applied the UXPD method to a simple I2 molecule to determine its structure ‒in other words, its internuclear distance ‒in the alignment-laser field In this Article, we report on the profile of I 2p photoelectron diffraction from I2 molecules with a higher degree of alignment compared with our previous work[14], which was obtained using XFEL pulses from SACLA. We have established that the internuclear distance of I2 in the laser field is slightly elongated relatively to the equilibrium internuclear distance
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