Abstract
Development of attosecond laser technology allows us to measure electron dynamics such as photoionization delays between different species or electronic states. In general, the measured photoionization phase is a mixture of the spectral phase of the extreme ultraviolet (XUV) pulse and the atomic phases inherent to the optical transitions. Hence, it is difficult to disentangle these phases independently. Here we separate these phases by using an XUV attosecond pulse train containing both even and odd harmonic orders, generated by an 800- and 400 nm laser pulse, in the presence of the infrared 800-nm pulse. We measure the photoelectron angular distributions as a function of two independently controlled delays, the XUV-IR and the 800--400 nm delays, with attosecond time resolution. We analyze the photoelectron angular distributions to determine the relative amplitudes and phases of each angular momentum component. Using an in situ technique, we determine the phases of the harmonic orders and thereby completely determine the atomic phases. Using the obtained atomic phases and amplitudes, we reconstruct the real and imaginary parts of the continuum wave functions associated with three individual photoionization pathways.
Highlights
An optical transition is characterized by the complex transition probability amplitude d
Using the RABBIT experiments alone and without calculations [4,5] or reference atoms [9], it is difficult to disentangle the harmonic phase from the atomic phase as well as further decomposing the atomic phase into the phases of individual transition moments
The atomic phases are relevant to the transition dipole moment and are independent of T2ω, while the harmonic phases of H13, H14, and H15 depend on T2ω
Summary
An optical transition is characterized by the complex transition probability amplitude d. Using the RABBIT experiments alone and without calculations [4,5] or reference atoms [9], it is difficult to disentangle the harmonic phase from the atomic phase as well as further decomposing the atomic phase into the phases of individual transition moments Another approach for attosecond dynamics and pulse measurements utilizes the electron recollision process which is the mechanism underlying attosecond XUV pulse generation [10]. The dual waveplate rotates the polarization of the ω pulse to make it parallel to that of the 2ω These beams are focused into an argon pulsed gas jet in a vacuum chamber to generate the XUV pulse in which odd and even harmonic orders of the fundamental frequency are produced. We measure the spectra of the XUV pulse by using a flat-field grating (Hitachi) and a microchannel plate
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