Spontaneous emission of positronium negative ions from polycrystalline tungsten surfaces

Spontaneous Emission of Positronium Negative Ions from Tungsten (100) Surface

“…Recently, we have observed Psformed by a new mechanism: spontaneous emission from polycrystalline tungsten surface [6][7][8]. In the present work, we have extended the study to the emission from tungsten single crystal.…”

Experiments on positronium negative ions

“…18) [119], indicating the adsorbate coverage of the target surface was reduced as a consequence the improved vacuum condition.…”

“…The base pressure of the chamber has been improved to be 3 × 10 −8 Pa.Source: Reprinted from[119].© 2008, with permission from Elsevier. m is the rest mass of the electron, c is the speed of light in vacuum and θ is the angle of deviation from the direction of the Ps − momentum.…”

Metallic electrical transport in inter-graphitic planes of an individual tubular carbon nanocone

“…The work function for CNT TCC is assumed to be 4.7 eV, which is a typical value for the work function of a carbon nanotube [17]. Work functions W (for W) and Au (for Au) are assumed to be 5.22 eV and 5.15 eV, respectively [18,19], which indicates barrier heights ( = TCC − W(Au) ) of 0.52 eV for the W-TCC tip junction and 0.45 eV for the Au-TCC bottom junction. The Pt catalyst particle on the tip of the TCC, as shown in figure 2(a), make good contact both with the W tip and the TCC, and has a rather similar work function (5.25 eV) to that of metal W [20], which introduces little modification (from 0.52 to 0.55 eV) to the barrier height of the W-TCC tip junction.…”

“…The electrical conductivity of graphite crystal had been measured to show that the resistivity ρ (4 × 10 −5 cm) along the direction of hexagonal plane is about 10 3 times lower than the resistivity ρ ⊥ (4 × 10 −2 cm) perpendicular to the hexagonal plane [25]. ρ increases exponentially with rising temperature, representing a metallic behavior; while ρ ⊥ falls with increasing temperature, showing a typical semiconducting behavior [18]. But in another previous study of inter-sheet transport in graphite, it was shown that intersheet resistivity ρ ⊥ is proportional to temperature, which verifies its metallic properties, even though the value of ρ ⊥ is of the same order with that of semiconductor [26].…”