Probing the longitudinal momentum spread of the electron wave packet at the tunnel exitClaudio Cirelli, Adrian N. Pfeiffer, Alexandra S. Landsman, Mathias Smolarski, Darko Dimitrovski, Lars B. Madsen and Ursula KellerEPJ Web of Conferences, 41 (2013) 02017DOI: https://doi.org/10.1051/epjconf/20134102017