Initial velocity of secondary ions from XY-TOF technique, simultaneous calibration by residual gas ionization

• Published in: International journal of mass spectrometry Vol. 231; no. 1; pp. 51 - 58
• Main Authors: Jalowy, T., Weber, Th, Dörner, R., Farenzena, L., Collado, V.M., da Silveira, E.F., Schmidt-Böcking, H., Groeneveld, K.O.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 2004
• Subjects: Initial velocity; Position sensitive detector; Secondary ion desorption; Time-of-flight; XY-TOF; Initial velocity; Secondary ion desorption; XY-TOF; Position sensitive detector; 34.50.Dy; 39.90+d; Time-of-flight
• ISSN: 1387-3806; 1873-2798
• DOI: 10.1016/j.ijms.2003.09.007

A crucial parameter to distinguish the prompt secondary ion emission from surfaces after particle impact from the delayed one is
T
0(
m/
q), the time-of-flight (TOF) of ions with a given mass
m and charge
q “emitted” with zero velocity. This quantity is also an important reference for the measurement of prompt ion emission velocity distribution.
Presented is a novel and accurate method to determine
T
0(
m/
q), based on position sensitive
XY-TOF analysis of residual gas ionization along the projectile trajectory, which is a low-pressure version of the traditional cloud chamber technique. Measurements using a mixture of He, Ne and Ar gases at low pressure (10
−5
mbar) were performed to illustrate this new
T
0-gas target calibration method. Secondary ion emission of H
n
+, C
n
H
n
+ and Li
+ ions from C, Al and LiF targets, bombarded by MeV Ar
0 and N
0 projectiles, is analyzed. It is found that, in contrast to Li
+, hydrogen and hydrocarbon ions are always promptly emitted. The initial velocity distribution of H
2
+ is determined and discussed.