Multiphoton Ionization Of Xe Research Articles

Theoretical study of spin polarization in multiphoton ionization of Xe

Spin polarization in the multiphoton above-threshold ionization of 5p3/2- and 5p1/2-electrons of Xe with intense 395nm, circularly polarized laser pulses, is investigated theoretically. For this purpose, we solve the time-dependent Schrödinger equation on the basis of spherical spinors. We, thus, simultaneously propagate the spin-up and spin-down single-active-electron wave packets, driven by the laser pulses in the ionic potential, which includes the spin-orbit interaction explicitly. The present theoretical results are in good agreement with the recent experimental results [D. Trabert et al., Phys. Rev. Lett. 120, 043202 (2018)].

Spin and Angular Momentum in Strong-Field Ionization.

The spin polarization of electrons from multiphoton ionization of Xe by 395nm circularly polarized laser pulses at 6×10^{13} W/cm^{2} has been measured. At this photon energy of 3.14eV the above-threshold ionization peaks connected to Xe^{+} ions in the ground state (J=3/2, ionization potential I_{p}=12.1 eV) and the first excited state (J=1/2, I_{p}=13.4 eV) are clearly separated in the electron energy distribution. These two combs of above-threshold ionization peaks show opposite spin polarizations. The magnitude of the spin polarization is a factor of 2 higher for the J=1/2 than for the J=3/2 final ionic state. In turn, the data show that the ionization probability is strongly dependent on the sign of the magnetic quantum number.

Generation of subpicosecond vacuum ultraviolet pulses at 126 nm by using harmonics of a subpicosecond Ti:Sapphire laser

Subpicosecond vacuum ultraviolet (VUV) pulses at the wavelength of 126 nm have been generated in rare gases as a result of the 7th harmonic radiation of a subpicosecond Ti:Sapphire laser oscillating at 882 nm. The VUV harmonic intensity was optimized in Xe at the pressure of 1.2 Torr. The behavior of the harmonic emission was qualitatively reproduced by the classical nonlinear optics. The increase of the harmonic intensity was limited by multiphoton ionization of Xe.

Influence of multi-photon ionization of Xe on a XeF discharge induced by KrF laser irradiation

Excimer laser preionization induced by an external laser was investigated for XeF excimer laser discharge induced by a KrF laser, paying attention to the ionized species in the gas. Enhancement of amplified spontaneous emission (ASE) was observed for XeF gas discharge preionized by a KrF laser with and without its irradiation. In contrast, no ASE enhancement was observed for KrF gas discharge with KrF laser preionization. ASE enhancement was larger for the longer wavelength, which was close to the two-photon resonance of the Xe atom, when tunable KrF laser irradiation was used. These results indicate that multi-photon ionization of Xe atoms supplied the initial electrons to the laser-induced preionization.

Multiphoton ionization of Xe and Kr with intense 0.62- microm femtosecond pulses.

Multiphoton ionization of Xe and Kr is investigated with intense 0.62-\ensuremath{\mu}m pulses of 900, 90, and 22 fsec duration. Deviation from the scaling of lowest-order perturbation theory is observed. For the shortest pulses a modified Keldysh theory closely fits the experimental data for xenon. The importance of dynamic resonances and the shifting ionization potential is discussed.

Multiphoton ionization of Xe and several small molecules at 193 and 248 nm

Relative multiphoton ionization rates for Xe, NO, NO 2, N 2O, O 2, N 2, CO, CO 2, H 2O, SO 2, CF 3Cl, CF 3I, and C 2F 5I have been measured as a function of laser power at 193 and 248 nm. A weakly focused rare-gas—halogen excimer laser beam passes in front of the exit aperture of an ion drift tube, and ions formed in the laser beam are extracted by the drift field into a quadrupole mass spectrometer. Relative ionization rates varied among these molecules by more than six orders of magnitude. In several cases the ionization mechanism could be inferred from the ion fragmentation pattern, a knowledge of the single-photon spectroscopy of the molecule, and the power dependence of the ionization rate.

Resonantly enhanced multiphoton ionization of xenon: photoelectron enrgy analysis

Photoelectron energy distributions resulting from multiphoton ionization of Xe through the 6s, 6s', and 5d levels are reported. Ionization via the 6s state leaves Xe + approximately equally in the 2P 3 2 and 2P 1 2 final states, as opposed to the ≈ 1.6:1 branching ratio observed in single photon ionization.