Two-photon ionization and three-photon above-threshold ionization of argon

Technical Report · Sun Mar 01 04:00:00 EST 1998

DOI:https://doi.org/10.2172/573347· OSTI ID:573347

Bouhal, A; Hamoniaux, G; Mysyrowicz, A; Antonetti, A ^[1]; Breger, P; Agostini, P ^[2]; Constantinescu, R C; Muller, H G ^[3]; DiMauro, L F ^[4]

---

1. ENSTA-Ecole-Polytechnique, Palaiseau (France). Lab. d`Optique Appliquee
2. DSM-DRECAM CEA Saclay, Gif-sur-Yvette (France)
3. FOM-Inst. for Atomic and Molecular Physics, Amsterdam (Netherlands)
4. Brookhaven National Lab., Upton, NY (United States). Chemistry Dept.

Studies of nonlinear laser-matter interaction have been so far limited to wavelengths from the near ultraviolet to infrared, because of the low brightness of currently available sources outside this range. However nonlinear processes in the VUV/Soft X-ray domain would initiate multiphoton innershell spectroscopy, XUV nonlinear optics and applications of such processes to metrology. The probability of multiphoton transitions decreases rapidly with the number of photons involved. A typical two-photon bound-free transition has a rate of the order of .1 ps{sup {minus}1} at 10{sup 12} W.cm{sup {minus}2} and scales as the square of the intensity. Such an intensity is therefore required to saturate a two-photon transition with a 100 fs pulse. This is difficult to achieve with the present state-of-the-art techniques for producing intense XUV pulses. To the authors knowledge, only two cases of such transitions have been reported so far. The first one is a two-photon ionization of argon by the third harmonic of a KrF laser. Since the photon energy (15 eV) is just below the ionization energy (15.75 eV) for argon, the transition is quasi-resonant. The second case is a two-photon ionization of helium by the 9th harmonic of a Ti:S laser. In the latter case an autocorrelation measurement of the harmonic pulse has been reported. In the present work, the authors report on two-photon ionization of argon at 133 nm (9.3 eV) from the third harmonic of a frequency doubled Ti:S laser, and a three-photon above-threshold ionization involving two 9.3 eV photons and one 3.1 eV photon.

• Research Organization: Brookhaven National Lab., Upton, NY (United States)
• Sponsoring Organization: USDOE Office of Energy Research, Washington, DC (United States)
• DOE Contract Number: AC02-76CH00016
• OSTI ID: 573347
• Report Number(s): BNL--65161; ON: DE98002818
• Country of Publication: United States
• Language: English

Related Subjects

66 PHYSICS
ARGON
EXPERIMENTAL DATA
LASER RADIATION
MULTI-PHOTON PROCESSES
PHOTOIONIZATION