Technique of Professionally-Applied Physical Training of Students of Building Specialties by Means of Orienteering

The problems of optimization of the educational process of physical culture in a higher educational institution are considered. Attention is paid to the development of professionally applied physical qualities of students in building specialties. The question of professional training with means of orienteering is being raised. The authors proceed from the assumption that the use of means and methods of orienteering in the classroom will lead to an improvement in the indexes of physical qualities, functional training and the working capacity of the civil engineer. It is noted that orienteering, as a sport, has a direct applied transfer of motor and associated skills. It is emphasized that the competences formed at students can find application in labor activity of the building specialist. The conclusion is made that the technique used leads to changes in the morphofunctional and motor components of physical readiness for labor activity. The results of a comparative analysis of the experimental and control groups on the indexes of physical development, functional state and physical qualities peculiar to builders are presented. The authors dwell on the development and approbation of the methodology used directly in the physical training classes for building students. It is proved that orienteering is an applied sport for the building specialties of the university, the means of which lead to the development of the physical qualities of a civil engineer

Long-lasting XUV activation of helium nanodroplets for avalanche ionization

We study the dynamics of avalanche ionization of pure helium nanodroplets activated by a weak extreme-ultraviolet (XUV) pulse and driven by an intense near-infrared (NIR) pulse. In addition to a transient enhancement of ignition of a nanoplasma at short delay times $\sim200$~fs, long-term activation of the nanodroplets lasting up to a few nanoseconds is observed. Molecular dynamics simulations suggest that the short-term activation is caused by the injection of seed electrons into the droplets by XUV photoemission. Long-term activation appears due to electrons remaining loosely bound to photoions which form stable `snowball' structures in the droplets. Thus, we show that XUV irradiation can induce long-lasting changes of the strong-field optical properties of nanoparticles, potentially opening new routes to controlling avalanche-ionization phenomena in nanostructures and condensed-phase systems

Long-lasting XUV activation of helium nanodroplets for avalanche ionization

We study the dynamics of avalanche ionization of pure helium nanodroplets activated by a weak extreme-ultraviolet (XUV) pulse and driven by an intense near-infrared (NIR) pulse. In addition to a transient enhancement of ignition of a nanoplasma at short delay times ${\sim}200$  fs, long-term activation of the nanodroplets lasting up to a few nanoseconds is observed. Molecular dynamics simulations suggest that the short-term activation is caused by the injection of seed electrons into the droplets by XUV photoemission. Long-term activation appears due to electrons remaining loosely bound to photoions which form stable ‘snowball’ structures in the droplets. Thus, we show that XUV irradiation can induce long-lasting changes of the strong-field optical properties of nanoparticles, potentially opening new routes to controlling avalanche-ionization phenomena in nanostructures and condensed-phase systems

Novel Collective Autoionization Process Observed in Electron Spectra of He Clusters

The ionization dynamics of He nanodroplets irradiated with intense femtosecond extreme ultraviolet pulses of up to 10^13\u2009\u2009W/cm2 power density have been investigated by photoelectron spectroscopy. Helium droplets were resonantly excited to atomiclike 2p states with a photon energy of 21.4 eV, below the ionization potential (Ip), and directly into the ionization continuum with 42.8 eV photons. While electron emission following direct ionization above Ip is well explained within a model based on a sequence of direct electron emission events, the resonant excitation provides evidence of a new, collective ionization mechanism involving many excited atomiclike 2p states. With increasing power density the direct photoline due to an interatomic Coulombic decay disappears. It indicates that ionization occurs due to energy exchange between at least three excited atoms proceeding on a femtosecond time scale. In agreement with recent theoretical work the novel ionization process is very efficient and it is expected to be important for many other systems