Total Xe ion intensity vs laser intensities for linearly and circularly polarized lights on a log-linear plot. (a) The ion intensities are plotted as a function of the same laser energy for both polarizations. The laser intensity for linearly polarized light was estimated based on of Xe: . (b) The horizontal axis for the circularly polarized light is shifted by a factor of 0.66 in order to fit the intensity dependence for both polarizations. The total Xe ion dependencies for both polarizations were the same on the LP laser intensity scale (lower horizontal axis). The upper horizontal axis indicates the laser intensity for circularly polarized light.
TOF-mass spectra of anthracene ionized by circularly [(a) and (c)] and linearly [(b) and (d)] polarized lights at high [(a) and (b)] and low [(c) and (d)] laser intensities. and indicate the first and second charged molecular ions, respectively. (, ) indicate fragment ions. At high laser intensities [(a) and (b)], fragment ion intensities are higher under circularly polarized light. The original signal intensities for (c) and (d) are multiplied by 3 and 3.3, respectively. The presented laser intensities are scaled with the linearly polarized intensity (see Sec. II A). The original laser intensities for circularly polarized light, which are based on the input laser energy, are (a) and (c) .
(a) Laser intensity dependence of singly charged molecular ions and total ions. The total ions consist of all molecular and fragment ions. The horizontal scales are the same as those in Fig. 1(b). The same values in the total ion intensities were observed for both polarizations for all intensity ranges we examined. (b) Ion intensities are plotted on a scale of laser electric field.
Laser intensity dependence of (a) and [(b) and (c)] and . The scales for the horizontal axes are the same as those in Fig. 1. The ion intensities of small fragment ions were higher for circularly polarized light. The ion intensities of large fragment ions were lower for circularly polarized light than those for linearly polarized light in the higher laser intensities (see text). The ion intensities of were higher than those of for the circularly polarized light, while the ion intensities of were higher than those of for the linearly polarized light.
Ratios of fragment ions to (a) total ions and (b) . In the case of circularly polarized light irradiation, the ratios of fragment ions were higher in the ranges of higher than .
Angular distributions of ion intensities at 4.76 . The horizontal axis indicates the angle between the TOF direction and the laser polarization direction. All data were normalized to . Small fragment ions were ejected parallel to the laser polarization.
Fragmentation schemes of anthracene ion depending on the configurations between the long axis and the laser polarization direction. (a) Parallel and (b) perpendicular configurations. (a) The parallel molecules are ionized and are resonant with the laser field. The molecules are expected easily to dissociate. (b) The transition moment of the anthracene radical cation and the laser polarization axis are perpendicular to each other. The resonance condition doses not hold; therefore, molecular ions would survive.
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