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Omegatron investigation of hydrogen in an ultra-high vacuum system
Classified Abstracts
382
made of two types of omegatrons : one has been described by Klonfer and Schmidt and one which has been develoned starting from the Klopfer omegatron and which has an improved resolving power. , The analysis of gas in a picture tube can be done in several ways : (1) The omegatron is sealed to the tube after which the tube is pumped ; (2) The tube is provided with a break-seal prior to the pumping process of the tube. At a suitable moment an omegatron is sealed to the break-seal after which the omegatron volume is pumped and sealed from the pump ; and (3) A sealed tube is opened under vacuum. The last procedure is done by cementing a vertical tubulation to the neck of the picture tube with the aid of epoxy resin. Prior to this a hole has been bored ultra-sonically in the neck of the tube leaving about 0.5 mm of the glass wall. The vertical glass tubulation is connected to an omegatron and a pumping system. After the epoxy resin has hardened the system is pumped and baked at 400% during 15 h, after which a pressure of lO-8 torr is obtained. The valve to the pump is closed and with the aid of a magnetically operated iron weight the remaining glass wall is punched, after which the gas in the tube is analysed. With the aid of the methods (1) and (2), gas analyses have been done in bulb blanks and in complete tubes before and after evaporation of the getter. The gas in the finished tube only consists of methane and argon. During operation of the tube methane disappears very fast while hydrogen and nitrogen are released from the screen. The desorption speeds from the screen and the absorption speeds of the getter for both hydrogen and nitrogen have been measured during life from the increase in pressure during screen bombardment. (Germany) (Author) J. Van der Waal, 2nd Internat. Symp. residual gases in electron Nuovo Cimento (in press). tubes, Milan, (March 1963)
12.
Measurement of Low Pressures
12 : 22 885. Calibration of ultra-high vacuum gauges. (Great Britain) A pump is used to draw air through a series of very accurately machined holes and the gauge to be calibrated is coupled between the last hole and the pump. A McLeod vacuum gauge is coupled up further up the line of holes when the pressure is higher. The height of the mercury column in this reference gauge is read with a cathetometer. It is claimed by the National Research Corporation of Cambridge, Massachusetts, who offer this service, that the system can calibrate gauges on an absolute w. J. s. basis down to 10-O torr. (U.S.A.) Anon., New Scientist, 19 (350), August 1963, 248. 12 :47 On the residual pressures of Nat CO and H, over bulk getters of thorium and zirconium alloys. See Abstr. No. 973. The measurement of residual gases in electron tubes. No. 970.
14.
12 : 41 : 33 See Abstr.
Kinetic Theory of Gases
14 : 16 The adsorption of a binary gaseous system at low temperature. See Abstr. No. 892.
16.
Gases and Solids
16 : 37 : 41 886. The catalytic activity and structure of evaporated silver films used for the oxidation of carbon monoxide. (Great Britain). R. L. Moss, et. al., Trans. Faraday Sot., 59 (l), Jan. 1963, 216-229.
885-893
16 : 30 : 41 887. Surface potential study of the chemisorption of hydrogen and carbon monoxide on evaporated copper and gold films. (Great Britain) J. Pritchard, Truns. Faraday Sot., 59 (2), Feb. 1963, 437-452. 16 : 30 : 41 888. Some reactions of cyclohexene with hydrogen and deuterium on evaporated gold films. (Great Britain) J. Erkeleus, et. al., Trans. Faraday Sot., 59 (5), May 1963, 1181-1191. 16 : 30 : 41 889. Depletive adsorption of hydrogen and carbon monoxide on nickel oxide. (Great Britain) J. D. Cotton and P. J. Fensham, Trans. Faraday Sot., 59 (6), June 1963, 1444-1457. 16 890. Flow of adsorbable gases in a microporous medium. (Single sorbates and binary mixtures). (Great Britain) R. Ash, et al., Proc. Roy. Sot, 271 (1344), l-33. 16 : 33 891. Gas desorption efficiency under electron bombardment. Utaly) Low power electron bombardment of surfaces proves to be a very powerful technique for the investigation of gas-solid interactions at very low pressures. In particular, it provides means for clearly distinguishing between adsorbed gas on a surface and gas fluxes reaching the surface from the bulk. A quantitative analysis of our measurements indicates that the electron desorption efficiency may be strongly dependent on binding energy ; for a complete monolayer of weakly adsorbed gas, the efficiency is of the order of lO-4 to 1O-2 molecules/electron, whereas for strongly bound gas, it appears to be as low as lo-” to lO-B (Author) molecules/electron. (Switzerland) L. A. Petermann, 2nd Internat. Symp. residual gases in electron tubes, Milan, (March 1963), Nuovo Cimento (in press). 16 : 14 892. The adsorption of a binary gaseous system at low temperature. (Ztaly) It has been noted that the physical adsorption of condensable gases on cold surfaces is accompanied by the adsorption of other gases, which, if alone, are only adsorbed with difficulty. A few older results of experiments at 78”K, and not previously published, are given. The degassing of a Hopkins condenser warming up naturally, enabled the quantity of NI previously fixed at the low temperature to be estimated by means of an omegatron. This phenomenon has recently been studied by Schmidlin, Hetlinger and Gawin. Other experiments carried out at lower temperatures on a novel binary gaseous system under dynamic conditions lead to interesting conclusions. (Author) (France) D. A. Degras, 2nd Internat. Symp. residual gases in electron tubes, Milan, (March 1963), Nuovo Cimento (in press). 16 : 22 : 27 893. Omegatron investigation of hydrogen in an ultra-high vacuum system. (Great Britain) Prior to the tests, the system was baked and all electrodes extensively outgassed until a pressure of the order of lo-l0 torr was reached. Hydrogen of Reagent Research’ Grade was then leaked into the system until the pressure was increased to lo-’ torr. The following table records the ion currents (IO-‘*A) as given by the omegatron for the different mass numbers when operating with a beam current of 5pA. The two sets of values correspond respectively to the case of the Bayard-Albert gauge
Classified Abstracts being either in operation or not. It will be seen that the spectrum of the residual gas is considerably affected by the pumping action of the gauge. Mass No. 1 2 3 16 18 28 44
Source H H,f Ha+ CH4+ H,Q+ co+ COsf
Ion current (lo-IsA) Gauge off Gauge on 0.55 55 36 0.1 0.1
0.2 24 1.2 0.45 1.6 4.6 0.1
The author gives reasons molecules of CH,, Hz0 and hydrogen with the glass of *...~_-_-.. .I__lP ._ nyurogen useu is probabiy by the incandescent tungsten V. J. Mimeault,
for supposing that the contaminant CO are due to interaction of atomic the containing vessel. The atomic produced from moiecuiar hydrogen filament of the gauge. (U.S.A.) w. J. s. Vacuum, 13 (6), June 1963, 229-230.
16 : 41 894. Crystal field effects in the adsorption and desorption of oxygen at a nickel oxide surface. (Great Britain) The adsorption of oxygen on nickel oxide has been studied over the range of temperature from 20°C to 460°C. It is an activated process. The attainable coverage at 6 x lO-2 mm pressure ^,.““_” l L+,.....L iJL133GD rlU”ug‘l a iiiaxim-urn at 250°C. The CiXXiLlge 2: thi3 temperature is 10 per cent but it is only 1 per cent at 20°C. Illumination at 20°C of a surface carrying adsorbed oxygen gives rise to desotption, and experiments with filters show that the photo-activity is almost entirely confined to wavelengths between 650mp and 9OOmr. The kinetics of the photodesorption have been studied and the dependence on incident light intensity has been examined. Photodesorption at 20°C is more extensive when oxygen has been presorbed at room temperature (1 per cent coverage) than when it has been presorbed at higher temperatures (higher coverages). The absorption spectrum of nickel oxide is discussed and the correiation between the waveiengths active in photodesorption and those involved in internal d-d transitions of the Ni2+(d*) ion is emphasised. The changes in crystal field stabilization during chemisorption of oxygen on nickel ions in the three principal planes (lOO), (110) and (111) are outlined, and a model is presented which associates photodesorption with the change from six-fold to four-fold co-ordination initiated by absorption in the 3A2-ST1s band. The kinetics which follow from the The influence model are shown to conform to those observed. of coverage on photodesorption is discussed with reference to the role of NiS+ ions produced during oxygen chemisorption. (Great Britain) (Authors) J. Haber and F. S. Stone, Trans. Faraday Sot., 59 (l), Jan. 1963, 192-206. Surface contamination in kinetic pumping systems. No. 879. Sorption pumping at high and ultra-high vacua. No. 910.
16 : 11 See Abstr. 16 : 21 See Abstr.
16 : 22 Effect of adsorbed oxygen in measurements with ionization gauges. See Abstr. No. 920. Non-evaporatfng getters with surface dflfusion. See Abstr. No. 974.
adsorption
and
16 :47 pore-
894-899
383 18.
Gaseous
Electronics
18 : 33 895. Thermal recovery of inert gases ionicaily pumped into glass. (Italy) Inert gases (generally observed as common residuals in electron tubes) were ionically pumped into a glass surface and the snonm_~~~ taneous recovery observed with a mass spectrometer. The pumping was conducted under dynamic conditions such that a constant ion bombardment rate was maintained. The recovery rate was measured as a function of time after ending bombardment and was found to be related to this parameter by the expression : Rate at-“. The index n was found to decrease from - 1 at short pumping times to a lower value at long pumping times. The long pumping time values of n were observed to depend upon the pumping pressure, decreasing to -0.25 at pressures of lo-* tori-. This typical behaviour of recovery from metals (- 1 index) to that of “ pseudo equilibrium static nnmninn ” FP,.I\.,PIII ;n&.r> r0nrnA1rmrt i,U”‘~“‘6 “_“.W”, ‘-0.5 \ L”“‘“, ..IP_ “_I_ ‘~y’vuuc’v. An explanation of the recovery data is given in terms of thermal desorption from a heterogenity of capture sites near the glass surface. This is shown to agree with a previous theory of pumping into glass surfaces. (Great Britain) (Authors) G. P. Smeaton, J. H. Leek and G. Carter, 2nd Internat. Symp. residual gases in electron tubes, Milan, (March 1963), Nuovo Cimento (in press). 18 : 47 Interactions between ionizing discharges and getter films. See Abstr. No. 978. 18 : 31 : 52 Some effects of cathode material and surface nature on work function and sparking potentials in hydrogen. See Abstr. No. 933.
19. Radiation 19 896. Pulsed Laser operation in helium-neon mixtures. (Great Britain) In a previous paper, the authors reported pulsed infrared osciiiations in the after giow of a heiium-neon piasma at pressures of the order of 1 torr. The present communication describes results obtained at higher pressures. The gas mixture was excited by means of external ring electrodes to which were applied 1~ set pulses of up to 60 kV. Oscillation of the plasma occurs about 1~ set after the pulse with a half width of l-8 psec. Four wavelengths in the infrared were recorded, with a peak output of about 80 W and a mean power of about 25 mW. The discharge becomes unstable if the total gas pressure exceeds 240 torr (neon partial pressure 5 torr). (Great Britain) W. J. S.
H. A. H. Boot, et al., Nature, 198 (4882): 25 May 1963, 773-774. 19 897. Energy emitted in spectral lines by a plasma at equilibrium. (U.S.A.) L. M. Biberman, et al., Optics & Spectrosc., 14 (3), March 1963, 176. 19 898. Luminescence of anthracene crystal obtained by sublimation in an oxygen atmosphere under irradiation. (U.S.A.) V. L. Zima and A. N. Faidysh, Optics & Spectrosc., 14 (3), March 1963, 198. 19 899. Luminescence kinetics of chromium luminors. M. Composite AlIOI.Ga20,-Cr system and magnesium spine1 activated by chromium. (U.S.A.) N. S. Tolstoy and Liu Shun-Fu, Optics di Spectrosc., 14 (3), March 1963, 202.
382
made of two types of omegatrons : one has been described by Klonfer and Schmidt and one which has been develoned starting from the Klopfer omegatron and which has an improved resolving power. , The analysis of gas in a picture tube can be done in several ways : (1) The omegatron is sealed to the tube after which the tube is pumped ; (2) The tube is provided with a break-seal prior to the pumping process of the tube. At a suitable moment an omegatron is sealed to the break-seal after which the omegatron volume is pumped and sealed from the pump ; and (3) A sealed tube is opened under vacuum. The last procedure is done by cementing a vertical tubulation to the neck of the picture tube with the aid of epoxy resin. Prior to this a hole has been bored ultra-sonically in the neck of the tube leaving about 0.5 mm of the glass wall. The vertical glass tubulation is connected to an omegatron and a pumping system. After the epoxy resin has hardened the system is pumped and baked at 400% during 15 h, after which a pressure of lO-8 torr is obtained. The valve to the pump is closed and with the aid of a magnetically operated iron weight the remaining glass wall is punched, after which the gas in the tube is analysed. With the aid of the methods (1) and (2), gas analyses have been done in bulb blanks and in complete tubes before and after evaporation of the getter. The gas in the finished tube only consists of methane and argon. During operation of the tube methane disappears very fast while hydrogen and nitrogen are released from the screen. The desorption speeds from the screen and the absorption speeds of the getter for both hydrogen and nitrogen have been measured during life from the increase in pressure during screen bombardment. (Germany) (Author) J. Van der Waal, 2nd Internat. Symp. residual gases in electron Nuovo Cimento (in press). tubes, Milan, (March 1963)
12.
Measurement of Low Pressures
12 : 22 885. Calibration of ultra-high vacuum gauges. (Great Britain) A pump is used to draw air through a series of very accurately machined holes and the gauge to be calibrated is coupled between the last hole and the pump. A McLeod vacuum gauge is coupled up further up the line of holes when the pressure is higher. The height of the mercury column in this reference gauge is read with a cathetometer. It is claimed by the National Research Corporation of Cambridge, Massachusetts, who offer this service, that the system can calibrate gauges on an absolute w. J. s. basis down to 10-O torr. (U.S.A.) Anon., New Scientist, 19 (350), August 1963, 248. 12 :47 On the residual pressures of Nat CO and H, over bulk getters of thorium and zirconium alloys. See Abstr. No. 973. The measurement of residual gases in electron tubes. No. 970.
14.
12 : 41 : 33 See Abstr.
Kinetic Theory of Gases
14 : 16 The adsorption of a binary gaseous system at low temperature. See Abstr. No. 892.
16.
Gases and Solids
16 : 37 : 41 886. The catalytic activity and structure of evaporated silver films used for the oxidation of carbon monoxide. (Great Britain). R. L. Moss, et. al., Trans. Faraday Sot., 59 (l), Jan. 1963, 216-229.
885-893
16 : 30 : 41 887. Surface potential study of the chemisorption of hydrogen and carbon monoxide on evaporated copper and gold films. (Great Britain) J. Pritchard, Truns. Faraday Sot., 59 (2), Feb. 1963, 437-452. 16 : 30 : 41 888. Some reactions of cyclohexene with hydrogen and deuterium on evaporated gold films. (Great Britain) J. Erkeleus, et. al., Trans. Faraday Sot., 59 (5), May 1963, 1181-1191. 16 : 30 : 41 889. Depletive adsorption of hydrogen and carbon monoxide on nickel oxide. (Great Britain) J. D. Cotton and P. J. Fensham, Trans. Faraday Sot., 59 (6), June 1963, 1444-1457. 16 890. Flow of adsorbable gases in a microporous medium. (Single sorbates and binary mixtures). (Great Britain) R. Ash, et al., Proc. Roy. Sot, 271 (1344), l-33. 16 : 33 891. Gas desorption efficiency under electron bombardment. Utaly) Low power electron bombardment of surfaces proves to be a very powerful technique for the investigation of gas-solid interactions at very low pressures. In particular, it provides means for clearly distinguishing between adsorbed gas on a surface and gas fluxes reaching the surface from the bulk. A quantitative analysis of our measurements indicates that the electron desorption efficiency may be strongly dependent on binding energy ; for a complete monolayer of weakly adsorbed gas, the efficiency is of the order of lO-4 to 1O-2 molecules/electron, whereas for strongly bound gas, it appears to be as low as lo-” to lO-B (Author) molecules/electron. (Switzerland) L. A. Petermann, 2nd Internat. Symp. residual gases in electron tubes, Milan, (March 1963), Nuovo Cimento (in press). 16 : 14 892. The adsorption of a binary gaseous system at low temperature. (Ztaly) It has been noted that the physical adsorption of condensable gases on cold surfaces is accompanied by the adsorption of other gases, which, if alone, are only adsorbed with difficulty. A few older results of experiments at 78”K, and not previously published, are given. The degassing of a Hopkins condenser warming up naturally, enabled the quantity of NI previously fixed at the low temperature to be estimated by means of an omegatron. This phenomenon has recently been studied by Schmidlin, Hetlinger and Gawin. Other experiments carried out at lower temperatures on a novel binary gaseous system under dynamic conditions lead to interesting conclusions. (Author) (France) D. A. Degras, 2nd Internat. Symp. residual gases in electron tubes, Milan, (March 1963), Nuovo Cimento (in press). 16 : 22 : 27 893. Omegatron investigation of hydrogen in an ultra-high vacuum system. (Great Britain) Prior to the tests, the system was baked and all electrodes extensively outgassed until a pressure of the order of lo-l0 torr was reached. Hydrogen of Reagent Research’ Grade was then leaked into the system until the pressure was increased to lo-’ torr. The following table records the ion currents (IO-‘*A) as given by the omegatron for the different mass numbers when operating with a beam current of 5pA. The two sets of values correspond respectively to the case of the Bayard-Albert gauge
Classified Abstracts being either in operation or not. It will be seen that the spectrum of the residual gas is considerably affected by the pumping action of the gauge. Mass No. 1 2 3 16 18 28 44
Source H H,f Ha+ CH4+ H,Q+ co+ COsf
Ion current (lo-IsA) Gauge off Gauge on 0.55 55 36 0.1 0.1
0.2 24 1.2 0.45 1.6 4.6 0.1
The author gives reasons molecules of CH,, Hz0 and hydrogen with the glass of *...~_-_-.. .I__lP ._ nyurogen useu is probabiy by the incandescent tungsten V. J. Mimeault,
for supposing that the contaminant CO are due to interaction of atomic the containing vessel. The atomic produced from moiecuiar hydrogen filament of the gauge. (U.S.A.) w. J. s. Vacuum, 13 (6), June 1963, 229-230.
16 : 41 894. Crystal field effects in the adsorption and desorption of oxygen at a nickel oxide surface. (Great Britain) The adsorption of oxygen on nickel oxide has been studied over the range of temperature from 20°C to 460°C. It is an activated process. The attainable coverage at 6 x lO-2 mm pressure ^,.““_” l L+,.....L iJL133GD rlU”ug‘l a iiiaxim-urn at 250°C. The CiXXiLlge 2: thi3 temperature is 10 per cent but it is only 1 per cent at 20°C. Illumination at 20°C of a surface carrying adsorbed oxygen gives rise to desotption, and experiments with filters show that the photo-activity is almost entirely confined to wavelengths between 650mp and 9OOmr. The kinetics of the photodesorption have been studied and the dependence on incident light intensity has been examined. Photodesorption at 20°C is more extensive when oxygen has been presorbed at room temperature (1 per cent coverage) than when it has been presorbed at higher temperatures (higher coverages). The absorption spectrum of nickel oxide is discussed and the correiation between the waveiengths active in photodesorption and those involved in internal d-d transitions of the Ni2+(d*) ion is emphasised. The changes in crystal field stabilization during chemisorption of oxygen on nickel ions in the three principal planes (lOO), (110) and (111) are outlined, and a model is presented which associates photodesorption with the change from six-fold to four-fold co-ordination initiated by absorption in the 3A2-ST1s band. The kinetics which follow from the The influence model are shown to conform to those observed. of coverage on photodesorption is discussed with reference to the role of NiS+ ions produced during oxygen chemisorption. (Great Britain) (Authors) J. Haber and F. S. Stone, Trans. Faraday Sot., 59 (l), Jan. 1963, 192-206. Surface contamination in kinetic pumping systems. No. 879. Sorption pumping at high and ultra-high vacua. No. 910.
16 : 11 See Abstr. 16 : 21 See Abstr.
16 : 22 Effect of adsorbed oxygen in measurements with ionization gauges. See Abstr. No. 920. Non-evaporatfng getters with surface dflfusion. See Abstr. No. 974.
adsorption
and
16 :47 pore-
894-899
383 18.
Gaseous
Electronics
18 : 33 895. Thermal recovery of inert gases ionicaily pumped into glass. (Italy) Inert gases (generally observed as common residuals in electron tubes) were ionically pumped into a glass surface and the snonm_~~~ taneous recovery observed with a mass spectrometer. The pumping was conducted under dynamic conditions such that a constant ion bombardment rate was maintained. The recovery rate was measured as a function of time after ending bombardment and was found to be related to this parameter by the expression : Rate at-“. The index n was found to decrease from - 1 at short pumping times to a lower value at long pumping times. The long pumping time values of n were observed to depend upon the pumping pressure, decreasing to -0.25 at pressures of lo-* tori-. This typical behaviour of recovery from metals (- 1 index) to that of “ pseudo equilibrium static nnmninn ” FP,.I\.,PIII ;n&.r> r0nrnA1rmrt i,U”‘~“‘6 “_“.W”, ‘-0.5 \ L”“‘“, ..IP_ “_I_ ‘~y’vuuc’v. An explanation of the recovery data is given in terms of thermal desorption from a heterogenity of capture sites near the glass surface. This is shown to agree with a previous theory of pumping into glass surfaces. (Great Britain) (Authors) G. P. Smeaton, J. H. Leek and G. Carter, 2nd Internat. Symp. residual gases in electron tubes, Milan, (March 1963), Nuovo Cimento (in press). 18 : 47 Interactions between ionizing discharges and getter films. See Abstr. No. 978. 18 : 31 : 52 Some effects of cathode material and surface nature on work function and sparking potentials in hydrogen. See Abstr. No. 933.
19. Radiation 19 896. Pulsed Laser operation in helium-neon mixtures. (Great Britain) In a previous paper, the authors reported pulsed infrared osciiiations in the after giow of a heiium-neon piasma at pressures of the order of 1 torr. The present communication describes results obtained at higher pressures. The gas mixture was excited by means of external ring electrodes to which were applied 1~ set pulses of up to 60 kV. Oscillation of the plasma occurs about 1~ set after the pulse with a half width of l-8 psec. Four wavelengths in the infrared were recorded, with a peak output of about 80 W and a mean power of about 25 mW. The discharge becomes unstable if the total gas pressure exceeds 240 torr (neon partial pressure 5 torr). (Great Britain) W. J. S.
H. A. H. Boot, et al., Nature, 198 (4882): 25 May 1963, 773-774. 19 897. Energy emitted in spectral lines by a plasma at equilibrium. (U.S.A.) L. M. Biberman, et al., Optics & Spectrosc., 14 (3), March 1963, 176. 19 898. Luminescence of anthracene crystal obtained by sublimation in an oxygen atmosphere under irradiation. (U.S.A.) V. L. Zima and A. N. Faidysh, Optics & Spectrosc., 14 (3), March 1963, 198. 19 899. Luminescence kinetics of chromium luminors. M. Composite AlIOI.Ga20,-Cr system and magnesium spine1 activated by chromium. (U.S.A.) N. S. Tolstoy and Liu Shun-Fu, Optics di Spectrosc., 14 (3), March 1963, 202.