Frequency-resolved optical gating technique for retrieving the amplitude of a vibrational wavepacket.

Yasuo Nabekawa,Tomoya Okino,A Amani Eilanlou,Eiji J Takahashi,Katsumi Midorikawa,Yusuke Furukawa,Kaoru Yamanouchi

doi:10.1038/srep11366

Abstract

We propose a novel method to determine the complex amplitude of each eigenfunction composing a vibrational wavepacket of / molecular ions evolving with a ~10 fs time scale. We find that the two-dimensional spectrogram of the kinetic energy release (KER) of H+/D+ fragments plotted against the time delay of the probe pulse is equivalent to the spectrogram used in the frequency-resolved optical gating (FROG) technique to retrieve the complex amplitude of an ultrashort optical pulse. By adapting the FROG algorithm to the delay-KER spectrogram of the vibrational wavepacket, we have successfully reconstructed the complex amplitude. The deterioration in retrieval accuracy caused by the bandpass filter required to process actual experimental data is also discussed.

Highlights

We find that the two-dimensional spectrogram of the kinetic energy release (KER) of H+/D+ fragments plotted against the time delay of the probe pulse is equivalent to the spectrogram used in the frequency-resolved optical gating (FROG) technique to retrieve the complex amplitude of an ultrashort optical pulse
After describing the development of the FROG algorithm for the vibrational wavepacket, which we call ‘Matter-Wave FROG (MW-FROG)’, we report on the implementation of MW-FROG for a modeled vibrational wavepacket and discuss the accuracy of the retrieved data
We have proposed the MW-FROG method to retrieve the vibrational wavepacket amplitude of aν generated in the ground electronic state of a H+2 /detection of H+ (D+)2 molecule based on the theoretical model of photoexcitation from the bound ground state to the repulsive excited state

Summary

Experimental scheme

We will need a filter to eliminate the frequency components unnecessary for determining the wavepacket amplitude from the target spectrogram in our MW-FROG measurement We conclude that the MW-FROG algorithm is sufficiently reliable to resolve the aν-phase modulation with a depth larger than ~120 mrad even when the delay-KER spectrogram is degraded to have a finite KER resolution and noise This is due to the extraction of the relevant phase information contained in the beat frequency peaks by the bandpass filter.

Author Contributions

Findings

Additional Information