Chemistry Reference
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pathways in both neutral and ionic dissociation processes of C
60
under laser
irradiation.
C
60
þ
nhv
!
C
58
þ
C
2
fragmentation
ð
neutrals
Þ
ð
7
:
1a
Þ
C
60
Þ
!
C
58
þ
e
fragmentation
!ð
C
2
þ
ð
ions
Þ
ð
7
:
1b
Þ
C
60
e
!
#
þ
delayed ionization
ð
7
:
1c
Þ
C
58
#
þ
C
2
delayed fragmentation
ð
7
:
1d
Þ
C
56
þ
C
2
sequential fragmentation
ð
7
:
1e
Þ
C
60
2n
þ
e
!
C
2n
þ
fragmentation via C
2n
loss
ð
7
:
1f
Þ
C
56
þ
e
C
58
þ
nhv
!
C
2
þ
photofragmentation of neutral
fragments
ð
7
:
1g
Þ
C
58
þ
C
56
þ
nhv
!
C
2
photofragmentation of ionic
fragments
ð
7
:
1h
Þ
For the case of 355 nm laser irradiation, we found number n in process
(7.1a) to be 2. Since the ionization potential of C
60
(7.6 eV) is higher than
two-photon excitation energy of 355 nm (6.98 eV), neutral processes (7.1a)
will be more significant than ionization processes (7.1b-f) at 355 nm laser
irradiation. After above C
2
-loss processes, C
2n
H
2
polyynes are formed via
following polymerization and hydrogenation of C
2x
and C
2x
H radicals in
hexane or methanol solution.
xC
2
þ
M
!
C
2x
þ
M
ð
7
:
2
Þ
C
2x
þ
H
þ
M
!
C
2x
H
þ
M
ð
7
:
3
Þ
C
2x
H
þ
H
þ
M
!
C
2x
H
2
þ
M
ð
7
:
4
Þ
C
2x
H
þ
C
2y
H
þ
M
!
C
2x
þ
2y
H
2
þ
M
ð
7
:
5
Þ
Here, M represents a third body solvent molecule, which is an acceptor of an
excess energy released in each three-body recombination reaction. Hydrogen
atoms in reactions (7.3) and (7.4) must be supplied from either photo-
dissociation of solvent or H-atom abstraction reaction from solvent.
Kato et al. [24] have recently made a mass spectroscopic study on the
formation of C
2n
H
2
and C
2n
D
2
(n
2-5) polyynes from graphite under
the presence of H
2
and D
2
in the gas phase. When the delay time of the
ionization pulse relative to the vaporization pulse was changed, two dis-
tinctly different mass patterns were found: rather non-selective signals of
C
n
(n
¼
¼
6-20) and C
n
H
m
(n
¼
3-20 and m
¼
1-4) at shorter delay times, while
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