The laser pulse width effect on the dis- sociation probability of CH4+ irradiated by an ultrafast laser has been investigated experimentally and theoretically. The femtosecond laser at 800 nm with an intensity of 8.0 ...The laser pulse width effect on the dis- sociation probability of CH4+ irradiated by an ultrafast laser has been investigated experimentally and theoretically. The femtosecond laser at 800 nm with an intensity of 8.0 × 1013 W/cm2 was used. The ob- served relative yield of the primary fragment ion CH3+ increases with increasing pulse width and tends to saturate when the pulse width is longer than 120 fs. The field-assisted dissociation (FAD) model and quasi-classical trajectory (QCT) calculation were ap- plied to predicting the dissociation probability of CH4+. The calculated probability is corrected with the mo- lecular orientation effect and the spatial distribution of laser intensity. The modified results show that the dissociation requires at least 23 fs and saturates with long pulse widths (≥100 fs). The result is ap- proximately consistent with the experimental observa- tion.展开更多
Experimental investigations on the dis-sociation and ionization processes of NO2 in intensefields at wavelengths of 810, 405 and 270 nm, arepresented. The ratios of NO +2 /NO + are found to beindependent of the laser ...Experimental investigations on the dis-sociation and ionization processes of NO2 in intensefields at wavelengths of 810, 405 and 270 nm, arepresented. The ratios of NO +2 /NO + are found to beindependent of the laser intensity at these threewavelengths, but show strong dependence on thewavelengths. Longer wavelength produces a largerparent-ion yield in comparison with 405 nm. Peakprofiles of all the fragment ions clearly show little ki-netic energy releasing during the dissociation. Frag-ment ions are suggested to be produced from disso-ciation of the field ionized parent ions. Our resultsindicate that laser pulse wavelengths are the mostimportant parameters in ionization-fragmen- tationprocess of polyatomic molecules in intense field otherthan the laser intensity.展开更多
文摘The laser pulse width effect on the dis- sociation probability of CH4+ irradiated by an ultrafast laser has been investigated experimentally and theoretically. The femtosecond laser at 800 nm with an intensity of 8.0 × 1013 W/cm2 was used. The ob- served relative yield of the primary fragment ion CH3+ increases with increasing pulse width and tends to saturate when the pulse width is longer than 120 fs. The field-assisted dissociation (FAD) model and quasi-classical trajectory (QCT) calculation were ap- plied to predicting the dissociation probability of CH4+. The calculated probability is corrected with the mo- lecular orientation effect and the spatial distribution of laser intensity. The modified results show that the dissociation requires at least 23 fs and saturates with long pulse widths (≥100 fs). The result is ap- proximately consistent with the experimental observa- tion.
文摘Experimental investigations on the dis-sociation and ionization processes of NO2 in intensefields at wavelengths of 810, 405 and 270 nm, arepresented. The ratios of NO +2 /NO + are found to beindependent of the laser intensity at these threewavelengths, but show strong dependence on thewavelengths. Longer wavelength produces a largerparent-ion yield in comparison with 405 nm. Peakprofiles of all the fragment ions clearly show little ki-netic energy releasing during the dissociation. Frag-ment ions are suggested to be produced from disso-ciation of the field ionized parent ions. Our resultsindicate that laser pulse wavelengths are the mostimportant parameters in ionization-fragmen- tationprocess of polyatomic molecules in intense field otherthan the laser intensity.
