Reactions between Cold CH x + and Slow H and H 2
Abstract Using the combination of a linear 22-pole ion trap (22 PT) and a coaxial beam of hydrogen atoms, H abstraction from CH x + ( x =1, 4 and 5) has been studied. The temperature of the trap, T 22 PT , can be varied between 10 K and 300 K. The velocity distribution of the neutral target beam can...
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Published in | Zeitschrift für physikalische Chemie (Neue Folge) Vol. 225; no. 5; pp. 475 - 492 |
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Main Authors | , , , , |
Format | Journal Article |
Language | English |
Published |
01.05.2011
|
Online Access | Get full text |
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Summary: | Abstract
Using the combination of a linear 22-pole ion trap (22 PT) and a coaxial beam of hydrogen atoms, H abstraction from CH
x
+
(
x
=1, 4 and 5) has been studied. The temperature of the trap,
T
22 PT
, can be varied between 10 K and 300 K. The velocity distribution of the neutral target beam can be changed by cooling the accommodator (
T
ACC
=10–300 K) and using the focusing features of one or two hexapole magnets. The resulting velocity distributions are characterized by time-of-flight measurements. With the same setup, reactions of mass selected stored ions with a cold effusive beam of H
2
molecules have been measured with the discharge turned off. At temperatures of interstellar space, H-abstraction from CH
+
is efficient. CH
4
+
reacts five times faster with H than with H
2
at 50 K. In contradiction to
ab initio
calculations and to the established proton affinity of methane, CH
5
+
is slowly destroyed in collisions with H in our trap, even at 10 K. Some first results for collisions between CH
x
+
and D atoms are reported. For
x
=1, H–D exchange is quite efficient, even though it is in competition with the exothermic abstraction reaction. For
x
=4, H-abstraction,
i.e.
formation of HD molecules, dominates. Deuteration of CH
5
+
is measured to be very slow. |
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ISSN: | 0942-9352 2196-7156 |
DOI: | 10.1524/zpch.2011.0118 |