Effects of Involved Laser Photons on Radiation and Electron-Positron Pair Production in one Coherence Interval in Ultra Intense Lasers.

Electron radiation and γ photon annihilation are two of the major processes in ultra intense lasers (UIL). Understanding their behavior in one coherence interval (CI) is the basis for UIL-matter interaction researches. However, most existing analytic formulae only give the average over many CIs. Present understanding of these two multi-photon processes in one CI usually assume that they emit forward and their spectra have a cutoff at the energy of the electron/γ. Such assumptions ignore the effects of involved laser photons (EILP). We deduced the formulae for these two processes in one CI with EILP included and give the conditions for the EILP to be significant. Strong EILP introduces new behaviors into these two processes in one CI, such as large angle emission and emit particles above the usually assumed cutoff. Simulations show that the EILP would be significant when laser intensity reaches 2 × 1022 W/cm2, which is within the reach of state-of-art lasers.

[Experimental study of soft X-ray radiation in the interaction of circularly polarized femtosecond-laser-pulse with low pressure xenon].

Using flat-field grating Spectrometer, the ions lines with wavelength between 5 and 60 nm were measured, which were produced by the interaction of circularly polarized 35 femtosecond ultraintense and ultrashort laser-pulse with 5 mm length xenon at the pressure 2 and 3 kPa respectively. The highest transition is the XeVIII: 4d10 5s(2 S1/2)--4d9 5s5p('P3/2) line at wavelength 17.0856 nm at 2 kPa and 3 kPa, the highest transition is 11.343 nm line of XeVII 4d10 5s2(1S0)--4d9 5s5f(3P1) transition. The xenon is ionized to XeVII, XeVIII and XeIX at both pressure.