Observation of monoenergetic electrons from two-pulse ionization injection in quasilinear laser-wakefields by von der Leyen, M, Holloway, J, Ma, Y, Campbell, PT, Aboushelbaya, R, Qian, Q, Antoine, AF, Balcazar, M, Cardarelli, J, Feng, Q, Fitzgarrald, R, Hou, BX, Kalinchenko, G, Latham, J, Maksimchuk, AM, McKelvey, A, Nees, J, Ouatu, I, Paddock, R, Spiers, B, Thomas, AGR, Timmis, R, Krushelnick, K, Norreys, PA