The double ionization of helium in the strong-field limit has been studied using an electron-ion coincidence technique. The observed double ionization electron energy spectra differ significantly from the single ionization distributions. This gives new support to the rescattering model of double ionization and explicitly reveals the role of backward electron emission following the e-2e ionizing...

We quantify sequential and nonsequential contributions in two-photon double ionization of helium atoms by intense ultrashort extreme-ultraviolet pulses with central photon energies ℏω_{ctr} near the sequential double-ionization threshold. If the spectrum of such pulses overlaps both the sequential (ℏω>54.4 eV) and nonsequential (ℏω<54.4 eV) double-ionization regimes, the sequential and nonseque...

A surface ionization (SI) source was designed and constructed for ion mobility spectrometry (IMS). Compared with a conventional (63)Ni source, the surface ionization source is as simple and reliable, has an extended dynamic response range, is more selective in response, and does not have regulatory problems associated with radioactive ionization sources. The performance of this SI-IMS was evalu...

The ionization chambers are widely utilized in diagnostic radiology quality control and dosimetry. They are simple to use, and can be found commercially in various types depending on their applications. They are the recommended devices for the determination of the beam qualities in mammographic range. To assure the reliability of the measurements, the stability of the response of the ionization...

Time-dependent close-coupling, R-matrix double pseudo-states and distorted-wave methods are used to calculate the electron-impact double ionization cross section for the 1s22s2 ground state of the Be atom. At 1.5 times the double ionization threshold energy, the first two non-perturbative methods predict a cross section of approximately 1.0 × 10−18 cm2 for the direct double ionization of the 2s...

We report a novel experimental technique for the comparison of ionization processes in ultrafast laser pulses irrespective of pulse ellipticity. Multiple ionization of xenon by 50 fs 790 nm, linearly and circularly polarized laser pulses is observed over the intensity range 10 TW/cm to 10 PW/cm using Effective Intensity Matching (EIM), which is coupled with Intensity Selective Scanning (ISS) to...

We have studied ionization of alkali-metal Rydberg atoms by blackbody radiation (BBR). The results of theoretical calculations of ionization rates of Li, Na, K, Rb and Cs Rydberg atoms are presented. The calculations have been performed for nS, nP and nD states for principal quantum numbers n=8-65 at ambient temperatures of 77, 300 and 600 K. The calculations take into account the contributions...

We study the field-ionization threshold behavior when a Rydberg atom is ionized by a short single-cycle pulse field. Both hydrogen and sodium atoms are considered. The required threshold field amplitude is found to scale inversely with the binding energy when the pulse duration becomes shorter than the classical Rydberg period, and, thus, more weakly bound electrons require larger fields for io...

Strong few-cycle lasers enable sequential ionization of more than one electron per optical half-cycle. Understanding these correlated electron ionization events is crucial in developing a model of ionization dynamics in few-cycle laser fields and describing the foundations of laser plasma generation [1]. We have developed an experimental setup capable of characterizing correlated ionization eve...