Wang, GuoliJin, ChengLe, Anh-ThuLin, Chii Dong2012-08-312012-08-312012-07-10http://hdl.handle.net/2097/14631We show that photoionization cross sections of atoms can be accurately extracted from the high-order-harmonic spectra generated by intense infrared lasers only if the degree of ionization in the gas medium is small, implying that for this purpose the high-order-harmonic generation spectra should be taken at low gas pressure and at low laser intensity experimentally.This Item is protected by copyright and/or related rights. You are free to use this Item in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you need to obtain permission from the rights-holder(s).http://rightsstatements.org/vocab/InC/1.0/PhotoionizationHigh-order-harmonic spectraInfrared lasersArticle (publisher version)