Chemistry Reference
In-Depth Information
FIGURE 14.10
Schematic potential energy surface for the CN/CH
3
CCCH
3
system
(adapted from
Reference 78
).
!
CH
2
¼
¼
ð
CH
3
Þ
þ
ð
:
Þ
C
C
NC
H
14
10d
!
CH
3
C
¼
C
¼
CH
2
þ
HCN
ð
14
:
10e
Þ
!
CH
3
C
¼
C
¼
CH
2
þ
HNC
ð
14
:
10f
Þ
We have carried out aCMB experiment at a collision energy of 20.8 kJ/mol
[78]. We observed reactive scattering signal at m/e
79, corresponding to
the ion C
5
H
5
N
þ
. A reactive signal was observed at lower m/e values between
78 and 74 as well, but the TOF spectra recorded at those values showed
identical patterns to the one at m/e
¼
79, thus implying that they derive from
dissociative ionization of the same species. Also, in this case, the adduct
C
5
H
6
N could not be observed. We also put a lot of effort into an attempt to
search for the methyl loss channel and checked for m/e
¼
65 (C
4
H
3
N
þ
).
Unfortunately, this channel could not be detected experimentally. Based on
the weak reactive scattering signal for the H-loss channel, the unfavourable
kinematics of the CH
3
-loss channel, and their predicted branching ratio (see
below), we estimate that data accumulation times of at least 50 h at the CM
angle is necessary to obtain a signal-to-noise ratio comparable to that of
the H-atom loss channel. Such a long accumulation time for a single TOF
spectrum makes the measurements of the LAB distributions at m/e
¼
¼
65
not feasible.
In
the LAB product angular distribution recorded at
50
. The
solid lines superimposed on the experimental results are the calculated
m/e
¼
78 is shown together with the TOF spectrum recorded at
Y
¼
curves when using the CM best-fit functions of
Figure 14.12
. The LAB
angular distribution of the heavy C
5
H
5
N fragment is relatively narrow. If we
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