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 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 Quantum Phenomena and the Mobility of Potassium Ions in Argon

1974 ◽  
Vol 27 (2) ◽  
pp. 227 ◽  
Author(s):  
RO Watts
Keyword(s):  
Alkali Metal ◽  
Pressure Dependence ◽  
Room Temperature ◽  
Quantum Mechanical ◽  
Alkali Metal Ions ◽  
Potassium Ions ◽  
Zero Field ◽  
Mechanical Methods ◽  
Quantum Phenomena ◽  
Reduced Mobility

Recent work on the mobilities of alkali metal ions in the noble gases has indicated that there is a pressure dependence of the zero-field reduced mobility. The possibility of temporarily bound dimmers being responsible for this pressure dependence is examined here by quantum mechanical methods for the case of potassium ions in argon and it is shown that the conditions needed for a small pressure dependence do exist at room temperature.

scholarly journals Testing the Obligations of Presence in Academia in the COVID-19 Era

2020 ◽  
Vol 12 (16) ◽  
pp. 6350 ◽  
Author(s):  
Clare Shelley-Egan
Keyword(s):  
Career Progression ◽  
Academic Life ◽  
Research System ◽  
Allocation Of Resources ◽  
Modus Operandi ◽  
Academic Mobility ◽  
Health Measures ◽  
Mobility Studies ◽  
Reduced Mobility

The COVID-19 crisis has given us a new, unprecedented impetus for thinking about the imperative of mobility in research. Travel and co-presence are widely accepted as being essential to career progression and promotion in academic life. Academics with fewer opportunities to travel find themselves at a significant disadvantage. COVID-19 and related public health measures have significantly limited the ability to be physically co-present in academia. Addressing obligations of co-presence in a less mobile world allows us to think concretely—and empathetically—about how to improve and extend virtual networking opportunities to those who have been marginalised with respect to research mobility. It also allows us to reflect on the role of reduced mobility and locality in how we think about and enact research. This article is informed and inspired by insights from research addressing academic mobility. I describe and discuss two prospects to productively work towards a new academic modus operandi characterised by limited opportunities for mobility. Furthermore, I highlight those issues and components that will require capacity building and a greater allocation of resources within the research system. In addition, I sketch out some pressing issues and questions for research mobility studies in a less mobile age going forward.

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 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.

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