title: Photon acceleration of ultrashort laser pulses by relativistic ionization fronts.
abstract: We present experimental results from the collision of weak ultrashort pulses with relativistic ionization fronts in copropagation and counterpropagation. The observed frequency upshifts of the probe pulses provide not only information about the electron density of the ionization front but also reveal the fine structure of the front. The connection between the correlation lengths for copropagation and counterpropagation and the longitudinal and transverse dimensions of the ionization front is also demonstrated thus showing the feasibility of using the frequency upshift experienced by short probe pulses to fully characterize relativistic ionization fronts and other relativistic coherent structures in laser-produced plasmas.
authors.affiliation: GoLP/Centro de Física de Plasmas, Instituto Superior Técnico, 1049-001 Lisboa, Portugal.
authors.forename: J M
authors.initials: JM
authors.lastname: Dias
authors.forename: N C
authors.initials: NC
authors.lastname: Lopes
authors.forename: L O
authors.initials: LO
authors.lastname: Silva
authors.forename: G
authors.initials: G
authors.lastname: Figueira
authors.forename: J T
authors.initials: JT
authors.lastname: Mendonça
authors.forename: C
authors.initials: C
authors.lastname: Stenz
authors.forename: F
authors.initials: F
authors.lastname: Blasco
authors.forename: A
authors.initials: A
authors.lastname: Dos Santos
authors.forename: A
authors.initials: A
authors.lastname: Mysyrowicz