title: Field dependent avalanche ionization rates in dielectrics.
abstract: From the pulse length dependence of the absorption of intense ultrashort laser pulses focused inside fused silica, we reveal the role field-assisted collisional ionization plays in the multiphoton ionization process. This constitutes a cold avalanche ionization mechanism that persists at pulse lengths considered too short for a traditional avalanche.
authors.affiliation: National Research Council of Canada, Ottawa, Canada, K1A 0R6.
authors.forename: P P
authors.initials: PP
authors.lastname: Rajeev
authors.forename: M
authors.initials: M
authors.lastname: Gertsvolf
authors.forename: P B
authors.initials: PB
authors.lastname: Corkum
authors.forename: D M
authors.initials: DM
authors.lastname: Rayner