Potassium surface

Figure A3.10.19 Variation of the initial sticking codFicient of N2 with increasing potassium surface concentration on Fe(lOO) at 430 K [50],...

C07-0006. Will a green photon (A = 515 nm) eject an electron from a potassium surface If so, what is the maximum kinetic energy of ejected electrons ... 

Effect of pressure Figure 2.40 shows the heat transfer coefficients for film boiling of potassium on a horizontal type 316 stainless steel surface (Padilla, 1966). Curve A shows the experimental results curve B is curve A minus the radiant heat contribution (approximate because of appreciable uncertainties in the emissivities of the stainless steel and potassium surfaces). Curve C represents Eq. (2-150) with the proportionality constant arbitrarily increased to 0.68 and the use of the equilibrium value of kG as given by Lee et al. (1969). 

Solid sodamide and potassium metal. Both of these substances undergo surface oxidation to give oxide films which may initiate explosions when the samples are handled. In the case of potassium, surface oxidation occurs even when the metal is stored under oil, and the act of paring off the oxide film with a knife may initiate an explosion. Samples of potassium which are heavily encrusted with oxide should not be used but should be carefully destroyed by adding the lumps to a large excess of propan-2-ol. Similarly, old or obviously encrusted (yellow) lumps of sodamide (Section 4.2.67) should not be ground in a pestle and mortar, but should be destroyed by mixing with solid ammonium chloride. 

Mehra, O.P. and Jackson, M.L., 1959. Constancy of the sum of mica unit cell potassium surface and interlayer sorption in vermiculite-illite clays. Proc. Soil Sci Soc. Am., 23 101-105. 

The mobility of potassium is smaller than that of cesium. The exposure of potassium metal to oxygen at room temperature leads to a complete oxidation of the metal, but, unlike cesium, the potassium atoms, during the oxidation, do not form a polyatomic layer on top of the oxide formed, but a layer of only one-atom thickness. Consequently the photoelectric current rises and continues to rise with the amount of oxide formed until a maximum is reached—when 4 X 10-4 g. of oxygen has been taken up/cm.2 of potassium surface 208)—after which it decreases... 

Light of frequency v is found to eject electrons of velocity ve from a clean potassium surface in vacuum. Which of the following is true concerning this phenomenon ... 

An experimental investigation of the lag in the photo-electric effect led to the conclusion that the sum of the lag of the Kerr effect in carbon bisulphide and the lag of the photo-electric effect from a potassium surface is not greater than 3(10 ) sec We read a paper on this research at the April meeting of the American Physical Society (abstract in press) and shall publish details later. 

The photoelectric effect illustrated for potassium metal in a partially evacuated tube. The work function required for the ejection of electrons from a potassium surface is 2.0 eV. Therefore, a photon of red light (hv = 1.77 eV) does not have sufficient energy to eject an electron. Photons of green or blue light, which have energies greater than 2 eV, can both eject electrons but the kinetic energies of the ejected electrons will differ. [Blatt Communications.]... 

Light with a wavelength of 425 nm fell on a potassium surface, and electrons were ejected at a speed of 4.88 X 10 m/s. What energy was expended in removing an electron from the... 

Fig.5.I9. ESCA surface sensitivity illustrated by progressing oxidation of a potassium surface. IL corresponds to 10 torrs of O2 exposure [5.32]...

In the study of condensed phase samples it is the outermost layers which are probed in the photoelectron experiments (down to Inm below the surface). The surface sensitivity is illustrated in Fig.5.19 for the case of slow oxidation of a potassium surface. Peaks due to potassium oxide and physisorbed O2 occur. A further example of surface studies is shown in Fig. 5.20 which shows ESCA spectra for a clean gold foil and for a gold foil contaminated by a faint fingerprint from a finger that had previously been in contact with silicone oil. Surface monitoring has been discussed in [5.33,34]. 

However, while this shows that the complex is likely to be produced during catalyst reduction, it is unlikely to remain on the catalyst surface at the temperatures where ammonia synthesis catalysts operate (>623 K). The rate of desorption of the alkali is strongly dependent on the heat of adsorption which, on carbon supports or single-crystal metal surfaces, decreases markedly with coverage, as shown for nickel in Fig 9.6. Similarly, for potassium on ruthenium the heat of desorption decreases from 112 6 = 0%) to 105 kJmol" (0 = 40%) while only a 5% potassium surface coverage remains after flash desorption of Ru(OOOl) at 1000 A simple calculation, based on a desorption frequency of i = 10 s" implies that for a heat of adsorption of 270 kJ moP the residence time on the surface at 773 K would only be... 

The addition of potassium to Fe single crystals also enliances the activity for ammonia synthesis. Figure A3.10.19 shows the effect of surface potassium concentration on the N2 sticking coefficient. There is nearly a 300-fold increase in the sticking coefficient as the potassium concentration reaches -1.5 x 10 K atoms cm ... 

Paal Z, ErtI G and Lee S B 1981 Interactions of potassium, nitrogen, and oxygen with polycrystalline iron surfaces Appl. Surf. Sc/. 8 231... 

Figure C2.10.5. Magnitude of the Fourier transfonn of tire /c-weighted absorjDtion fine stmcture k (/c) measured at tire Cu K edge for tire underiDotential deposition of Cu/Au(l 11) from 0.1 M KCIO +IO M HCIO +S x 10 M Cu (010 )2+10 M potassium salt of sulfate, chloride, bromide and a mixture of sulfate and chloride, for polarization of tire x-rays parallel to tire sample surface ( ) or parallel to tire surface nonnal (E (from [81]).

To the cold solution, add about 2 ml. of 10% potassium iodide solution. A brisk effervescence of nitrogen occurs, and iodobenzene separates, usually as drops so small that in spite of their density they float on the surface. 

Place 32 g. of potassium ethyl xanthate (Section 111,166) and 50 ml. of absolute ethyl alcohol in a 500 ml. round-bottomed flask provided with a double surface condenser. Add 32 g. (16-5 ml.) of ethyl iodide. No reaction appears to take place in the cold. Heat on a water bath for 3 hours a reaction sets in within 15 minutes and the yellow reaction mixture becomes white owing to the separation of potassium iodide. Add about 150 ml. of water, separate the lower layer, and wash it with water. Dry it with anhydrous calcium chloride or anhydrous calcium sulphate and distil from a 50 ml. Claisen flask. Collect the ethyl S-ethyl xanthate at 196-198°. The yield is 23 g. 

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