scholarly journals The Mobility of Li + Ions in Helium and Argon

1985 ◽  
Vol 38 (4) ◽  
pp. 587 ◽  
Author(s):  
RA Cassidy ◽  
MT Elford
Keyword(s):  
Thermal Equilibrium ◽  
Drift Tube ◽  
Cluster Ions ◽  
Zero Field ◽  
Number Density ◽  
Field Mobility ◽  
Mass Spectrometer System ◽  
Cluster Ion ◽  
Spectrometer System ◽  
Reduced Mobility

A drift tube-mass spectrometer system employing Bradbury-Nielsen shutters has been used to measure the mobility of Li + ions in He at 294 and 80 K and Li + ions in Ar at 294 K. The E/N range used was 3 to 80 Td (1 Td == 10 - 21 Y cm2). The zero field reduced mobility for Li + in He was found to be 22�81�0�11 cm2 y-1 s-I at 294 K and 19�64�0�29 cm2 y-1 s-I at 80 K. The value for Li+ in Ar at 294 K is 4�66�0�22 cm2 y-1 s-I. The reduced zero field mobility for the cluster ion Li +. He in He at 80 K and low values of E/ N was found to be 14�84 � 0�22 cm2 y -I s - I. The equilibrium constant for the formation and dissociation of Li + . Ar cluster ions at 294 K was obtained by fitting to the variation of the measured mobility with gas number density at low E/N values. The value obtained, corresponding to thermal equilibrium at 294 K, was (4�0.5)xlO- 19 cm3 .

scholarly journals The Mobility of H+3 and H+5 Ions in Hydrogen and the Equilibrium Constant for the Reaction H+3+2H2<=> H+5+H2 at Gas Temperatures of 195, 273 and 293 K

1974 ◽  
Vol 27 (6) ◽  
pp. 795 ◽  
Author(s):  
MT Elford ◽  
HB Milloy
Keyword(s):  
Equilibrium Constant ◽  
Zero Field ◽  
Hydrogen Ions ◽  
Mobility Data ◽  
Mass Spectrometer System ◽  
Spectrometer System ◽  
Reduced Mobility ◽  
Ion Species ◽  
Good Agreement ◽  
Gas Pressures

The mobilities of hydrogen ions in hydrogen have been measured by the Bradbury-Nielsen time-offlight method at temperatures of 195, 273 and 293 K, at pressures in the range O' 5-200 torr and at E/ N values ranging from 0�4 to 200 Td. The zero field reduced mobilities of H~ and H~ have been determined to be 1l�18�0�05 and 10'61�0'05cm2 s-1 V-1 at 293K, and 1l�18�0�05 and 10'53�0'05cm2 s-1V-1 at 273�2K respectively. At 194'5K the zero field reduced mobility of H~ was determined to be 10�40�0�05 cm2 s-1V-1 ? The thermal equilibrium constant K. for the reaction H~ + H2 + H2 +2 H~ + H2 was obtained by fitting the mobility data as a function of gas pressure. The values of K. obtained were 1�83�0�45 X 10-18, 2�8�0�7 X 10-18 and 1'6�0'6 x 10-16 cm3 at 293,273 and 195 K respectively. The reduced mobility of Hj as a function of E/N was derived for values of E/ N up to 200 Td from the data taken at gas pressures less than 2 torr and was found to be in good agreement with the data of Miller et al. (1968). The ion species present were identified by the addition of contaminants and by use of supplementary data taken with a drifttube- mass-spectrometer system. The energy for the dissociation of H~ into Hj and H2 was derived by the method of Eyring et al. (1936) and found to be 250� 50 meV.

scholarly journals Pressure Dependence and End Effects in Precision Ion Mobility Studies

1974 ◽  
Vol 27 (2) ◽  
pp. 211 ◽  
Author(s):  
MT Elford ◽  
HB Milloy
Keyword(s):  
Pressure Dependence ◽  
Zero Field ◽  
Surface Layers ◽  
End Effects ◽  
Pressure Limit ◽  
Fitting Procedure ◽  
Resonant States ◽  
Mobility Studies ◽  
Cluster Ion ◽  
Reduced Mobility

The mobilities of K + ions have been measured by the Bradbury-Nielsen method in He, Ar, H2 and N 2 at 293 K at pressures and E/Nvalues in the range 1�4-190 torr and 1-28 Td respectively. Three drift tubes were used with drift lengths of 3� 395, 9� 076 and 50�00 cm. The anomalous variation of the reduced mobility with E/ N at low values of E/ N reported by Elford (1971) has been shown to be due to the presence of charged surface layers on the first grid of the time-of-flight system. The dependence of the reduced mobility on pressure also reported by Elford has been confirmed, and an explanation of the pressure dependence in He, Ar and H2 is proposed in terms of the formation of ion-atom or ionmolecule complexes in orbiting resonant states. The zero-field reduced mobilities in the zero-pressure limit have been derived by a fitting procedure and found to be 21 �3 � O' 2, 2�64 � O� 02 and 12� 8 � O' 1 cm2 y-1 S-l for He, Ar and H2 respectively. The pressure dependence of the reduced mobility for K + ions in N2 is shown to be of a different form from the other gases investigated and to be due to the formation of the cluster ion K + . N2. The present data are consistent with the equilibrium constant of Beyer and Keller (1971) for the reaction K + + N2 + N2 +� K + . N2 + N2. The zero-field reduced mobility for K+ ions in N2 in the zero-pressure limit has been found to be 2�50�0�02 cm2 Y-1 s-1.

scholarly journals Ion?Molecule Reactions and Mobilities of SF3+ and SF5+ Ions in SF6 Gas

1993 ◽  
Vol 46 (6) ◽  
pp. 799 ◽  
Author(s):  
ZA Talib ◽  
M Saporoschenko
Keyword(s):  
Field Strength ◽  
Electric Field ◽  
Electric Field Strength ◽  
Drift Tube ◽  
Ion Source ◽  
Zero Field ◽  
Number Density ◽  
Mobility Data ◽  
Ion Molecule Reactions ◽  
Positive Ion

Positive ion-molecule reactions in 8F6 were studied in a static drift-tube mass spectrometer using electron impact at 100 eY as the ion source. The ratio of electric field strength to gas number density, E / N, was typically varied from 40-282 Td and pressure ranged from 0�1 to o� 8 Torr. The most important processes were found to be 8Ft + SF6 ---+ 8Ft + 8F6 + F2 and 8Ft + 8F6 ---+ (82Fg)+* ---+ 82Ft + F 2. The interaction potentials for the 8Ft and 8Ft ions in SF6 were also found by using the measured mobility data which were obtained using a pulsed-ion transit-time method. We found that the (12,4, a* = 0�1) core model was adequate to describe the mobility over the range of E / N studied. The zero-field reduced mobilities for 8Ft and 8Ft were determined to be 0�68 and 0�55cm2y-1 s- 1 respectively.

scholarly journals The Mobility of K+ Ions in Helium and Argon

1986 ◽  
Vol 39 (1) ◽  
pp. 25 ◽  
Author(s):  
RA Cassidy ◽  
MT Elford
Keyword(s):  
Mass Spectrometer ◽  
Drift Tube ◽  
Zero Field ◽  
Reduced Mobility

'A drift tube-mass spectrometer has been used to measure the mobility of K + ions in helium at 294 and 80 K over the EIN range 5-60 Td and in argon at 295 K over the EIN range 3-120 Td. The zero field reduced mobility KO for K + in He was determined to be 21� 14 � 0 . 11 cm 2 Y - 1 s - 1 at 294 K and 17 �32�0�26 cm2y-1 s-l at 80 K. The value of KO obtained for K+ in Ar at 295 K is 2 �640�0�013 cm2 y-1 s -1. The results are compared with those obtained in previous measurements.

scholarly journals Zero-field Mobility for Electrons in Dry and Humid Air

1975 ◽  
Vol 28 (2) ◽  
pp. 231 ◽  
Author(s):  
HB Milloy ◽  
ID Reid ◽  
RW Crompton
Keyword(s):  
Relative Humidity ◽  
Momentum Transfer ◽  
Water Vapour ◽  
Cross Section ◽  
Drift Tube ◽  
Zero Field ◽  
Humid Air ◽  
Dry Air ◽  
Field Mobility ◽  
Momentum Transfer Cross Section

The zero-field mobility of electrons in dry and humid air at 294 K has been studied with drift tube techniques. For air containing 1.5 % water vapour (50 % relative humidity) the zero-field mobility was found to be 8.4 � 0.2 X 105 cm s−l Td−l. The zero-field mobility of electrons in dry air (4.7 � 0.2 x 106 cm s−l Td−l) was deduced from measurements in which small quantities of CO2 Were added to reduce the electron energy. It is estimated that the momentum transfer cross section for electron–oxygen collisions, at near thermal energies, is at least four times smaller than it is for electron–nitrogen collisions.

FORMATION OF HELIUM-CLUSTER IONS CO2Hen+ (n≤15) IN A DRIFT TUBE COOLED BY LIQUID HELIUM

1996 ◽  
Vol 03 (01) ◽  
pp. 205-209 ◽  
Author(s):  
H. TANUMA ◽  
M. SAKAMOTO ◽  
N. KOBAYASHI
Keyword(s):  
Liquid Helium ◽  
Cluster Size ◽  
Drift Tube ◽  
Cluster Ions ◽  
Magic Numbers ◽  
Helium Atoms ◽  
Drift Field ◽  
Helium Cluster ◽  
Helium Gas ◽  
Cluster Ion

The formation of helium-cluster ion CO 2 He n+ (n≤15) has been observed when CO2+ ions are injected into a drift tube filled with helium gas cooled by liquid helium. The cluster sizes n = 5 and 14 are found to be magic numbers based on the drift-field dependence of the cluster size distribution. The structure of CO 2 He 14+ cannot be considered as the icosahedron, which is proposed as the structure of the cluster ions having twelve helium atoms surrounding the ionic core in our previous papers.

The Influence of Doping on the Etching of Si(111)

1986 ◽  
Vol 75 ◽  
Author(s):  
Harold F. Winters ◽  
D. Haarer
Keyword(s):  
Mass Spectrometer ◽  
Doping Level ◽  
Etch Rate ◽  
Plasma Reactors ◽  
Doping Effects ◽  
Mass Spectrometer System ◽  
Spectrometer System

AbstractIt has been recognized for some time that the doping level in silicon influences etch rate in plasma environments[1–8]. We have now been able to reproduce and investigate these doping effects in a modulated-beam, mass spectrometer system described previously [9] using XeF2 as the etchant gas. The phenomena which have been observed in plasma reactors containing fluorine atoms are also observed in our experiments. The data has led to a model which explains the major trends.

scholarly journals Dark matter freeze-in from semi-production

2021 ◽  
Vol 2021 (6) ◽  
Author(s):  
Andrzej Hryczuk ◽  
Maxim Laletin
Keyword(s):  
Dark Matter ◽  
Early Universe ◽  
Cross Section ◽  
Thermal Equilibrium ◽  
Indirect Detection ◽  
Production Mechanism ◽  
Number Density ◽  
Matter Production ◽  
Relic Density ◽  
Standard Formalism

Abstract We study a novel dark matter production mechanism based on the freeze-in through semi-production, i.e. the inverse semi-annihilation processes. A peculiar feature of this scenario is that the production rate is suppressed by a small initial abundance of dark matter and consequently creating the observed abundance requires much larger coupling values than for the usual freeze-in. We provide a concrete example model exhibiting such production mechanism and study it in detail, extending the standard formalism to include the evolution of dark matter temperature alongside its number density and discuss the importance of this improved treatment. Finally, we confront the relic density constraint with the limits and prospects for the dark matter indirect detection searches. We show that, even if it was never in full thermal equilibrium in the early Universe, dark matter could, nevertheless, have strong enough present-day annihilation cross section to lead to observable signals.

Measurement of changes in atmospheric Ar/N2 ratio using a rapid-switching, single-capillary mass spectrometer system

Tellus B ◽  
2004 ◽  
Vol 56 (4) ◽  
pp. 322-338 ◽  
Author(s):  
RALPH F. KEELING ◽  
TEGAN BLAINE ◽  
BILL PAPLAWSKY ◽  
LAURA KATZ ◽  
CHRIS ATWOOD ◽  
...  
Keyword(s):  
Mass Spectrometer ◽  
Mass Spectrometer System ◽  
Spectrometer System ◽  
Rapid Switching

A mass spectrometer system for analysis of polar stratospheric aerosols

2002 ◽  
Vol 73 (2) ◽  
pp. 446-452 ◽  
Author(s):  
J. Schreiner ◽  
C. Voigt ◽  
P. Zink ◽  
A. Kohlmann ◽  
D. Knopf ◽  
...  
Keyword(s):  
Mass Spectrometer ◽  
Mass Spectrometer System ◽  
Spectrometer System ◽  
Stratospheric Aerosols
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