The document investigates the effect of adding small amounts of molecular gases like hydrogen, oxygen, and nitrogen to an argon glow discharge used in mass spectrometry analysis. It finds that the addition of these gases can significantly impact ion signal intensities for the sputtered analyte, plasma gas, and trace gases. Specifically, it reports that the argon ion signal shows a dramatic decrease for all added gases. Meanwhile, the matrix ion signal initially increases but then decreases as the sputter rate is reduced. The study provides evidence that confirms results from previous modeling and experiments using different analytical techniques.

1. Effect of added molecular gases (H2
discharge on high resolution mass spectrometer ion signal intensities
Viktoria Weinstein1, Edward B.M. Steers1, Glyn Churchill
1 London Metropolitan University, 166-220 Holloway Road, London, N7 8DB, UK,
Phone/FAX: +44-(0)20-7133-2177/ +44-(0)20-71334375 E
2 EAGLabs, 6707 Brooklawn Parkway, Syracuse, NY 13211, US
1. Introduction
The effects of molecular gases (H2, O2, N2) in argon glow discharges
investigated by optical emission spectrometry (OES)1,2,3. In the current work,
mass spectrometry (MS) with Cu, Fe and Ti matrices, in order to understand
glow discharge can be significantly affected by the presence in the plasma
constituents. In these experiments, small fractions (0-2%v/v) of these gases
intensities for sputtered analyte, plasma gas and trace gases were recorded
Element GD Mass
Spectrometer
Thermo Fisher scientific
Fast Flow Glow
Discharge Plasma Source
2. Instrumentation
Fast flow tube allows routine
analysis and the ion transportation
time from the sample to the
cone is ~150us
IntegratedIntensity
This extensive study of the effects of molecular gases in glow discharges with
various matrices provides evidence which confirms results of previous modeling
and experimental investigations and will be linked to data obtained from similar
sources using time of flight mass spectrometry and optical emission
spectroscopy.
Acknowledgement
The authors wish to acknowledge support from the EU Marie Curie Research
Training Network Gladnet Contract MRTN
References
[1] V. D. Hodoroaba, E. B. M. Steers, V. Hoffmann and K. Wetzig, J. Anal. At.
Spectrom., 2001,
[2]
Spectrom., 2008,
[3]
T.
4. Discussion
 In general, the concentration of molecular gases observed in
analytical practice may be of the order of 0.2 % v/v or less. However
we have extended our observations to higher concentrations in order
to see the fuller picture and hence to gain a better understanding of
the processes.
 The observed changes in ion signals (in many cases, several
orders of magnitude) are much greater than those observed by OES. It
should be noted that with OES, the changes occur with the discharge
itself, whereas for MS there will almost certainly be changes in the
transport of the ions to the mass spectrometer.
 The Ar+ signal shows a dramatic fall for all added gases, the
magnitude depending very significantly on the matrix used (with H2,
greater with Fe and Ti than with Cu), and on the added gas – much
greater with hydrogen than with nitrogen and oxygen. These large
decreases contrast strongly with some OES results1, in which Ar II lines
increase in intensity (i.e. the population of excited Ar+ ions increases).
 In most cases, the matrix ionic signal initially increases with
added molecular gas, and then falls as the sputter rate decreases.
With hydrogen, there is a small decrease in the Ti+ signal but a
significant rise for Cu+, in general agreement with earlier results1.
2, O2, N2) in an argon analytical glow
discharge on high resolution mass spectrometer ion signal intensities
, Glyn Churchill2, Karol Putyera2, Martin Kasik2
220 Holloway Road, London, N7 8DB, UK,
71334375 E-mail: v.weinstein@londonmet.ac.uk
EAGLabs, 6707 Brooklawn Parkway, Syracuse, NY 13211, US
1. Introduction
discharges used for chemical analysis of solid samples have already been
work, complementary studies were made using advanced high resolution
understand better the mechanisms occurring in the plasma. Analytical results in
plasma gas of traces of such molecular gases, often arising from sample
gases were introduced into the discharge gas and the changes in ion signal
recorded for various samples.
Drop in sputter rates for Cu
1.E-17
1.E-15
1.E-13
1.E-11
1.E-09
1.E-07
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8
IntegratedIntensity
O2 conc. (% v/v).
Oxygen
40Ar++
40Ar16O+
16O16O+
16O+
40Ar+
63Cu+
63Cu16O+
63Cu++
Nitrogen
1.E-17
1.E-15
1.E-13
1.E-11
1.E-09
1.E-07
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6
IntegratedIntensity
H2 conc. (% v/v).
Hydrogen
40Ar++
40ArH+
40Ar+
63CuH+
63Cu+
63Cu++
3. Results
a. effect of various gases - Cu matrix
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
0 0.2 0.4 0.6 0.8 1 1.2 1.4
sputterrate[um/min]
X2 conc. (% v/v).
Drop in sputter rates for Cu
H2
N2
O2
1.E-17
1.E-15
1.E-13
1.E-11
1.E-09
1.E-07
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6
IntegratedIntensity
N2 conc. (% v/v).
Nitrogen
63Cu16N+
40Ar++
40Ar+
14N14N+
14N+
63Cu+
1.E-17
1.E-15
1.E-13
1.E-11
1.E-09
1.E-07
0 0.2 0.4 0.6 0.8 1
IntegratedIntensity
H2 conc. (% v/v).
Effect of H2 - Fe matrix
40Ar++40ArH+
40Ar+
54Fe+
54FeH+
54Fe++
1.E-17
1.E-15
1.E-13
1.E-11
1.E-09
1.E-07
0 0.2 0.4 0.6 0.8 1 1.2
IntegratedIntensity
H2 conc. (% v/v)
Effect of H2 - Ti matrix
48Ti+
50TiH+
40Ar++
40ArH+
40Ar+
b. Effect of Hydrogen - Various Matrices
5. Summary
This extensive study of the effects of molecular gases in glow discharges with
various matrices provides evidence which confirms results of previous modeling
and experimental investigations and will be linked to data obtained from similar
sources using time of flight mass spectrometry and optical emission
spectroscopy.
Acknowledgement
The authors wish to acknowledge support from the EU Marie Curie Research
Training Network Gladnet Contract MRTN-CT-2006-035459.
References
[1] V. D. Hodoroaba, E. B. M. Steers, V. Hoffmann and K. Wetzig, J. Anal. At.
Spectrom., 2001, 16 43-49.
[2] P. Šmíd, E.B.M. Steers, Z. Weiss, J.C. Pickering and V. Hoffmann, J. Anal. At.
Spectrom., 2008, 23, 1223-1233.
[3] S. Mushtaq, E.B.M. Steers, J.C. Pickering, P. Šmíd, V. Weinstein and
T. Gusarova, J . Anal. At. Spectrom. 2010, DOI: 10.1039/C0JA00013B