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We have studied strong-field laser-induced fragmentation of the benchmark hydrogen molecule in sub 5 fs near infrared (IR) pulses. As the pulse duration approaches a single cycle, the molecular response depends on the waveform of the pulse. For a particularly simple example of the waveform which is characterized by the carrier-envelope phase (CEP) – the CEP can be used as a control knob for the ensuing molecular dynamics.
In this kind of experiments a “CEP-locking” or “CEP-tagging” technique is typically employed. The latter method was used in our studies as demonstrated in this talk by two examples. The first involves the study of CEP control over pathway interference in strong-field dissociation of H2+ [1,2], where a molecular-ion beam was used as the target. In the second example we explore the formation of long-lived excited H fragments from the fragmentation of an H2 target. As predicted by theory [3,4], the measurements show that the CEP steers protons of H2+ (or excited-hydrogen fragments H2) one way or the other along the laser polarization. Moreover, the fragmentation yield itself depends on the CEP.

Others contributing to this work:
N.G. Johnson, M. Zohrabi, B. Berry, U. Ablikim, B. Jochim, T. Severt, K. J. Betsch, K.D. Carnes,
Shuo Zeng, F. Anis, J. Hernández, Yujun Wang, and B.D. Esry
1Supported by the Chemical Sciences, Geosciences and Biosciences Division, Office of Basic Energy Sciences, Office of Science, US Department of Energy