1. Fragmentation and lifetime of C60q+ trapped in a cone trap
S. Martin
J. Bernard
L. Chen
R. Brédy (post-doc at Kansas State Univ.)
B. Wei (PHD)
A. Salmoun, Marocco
Laboratoire de Spectrométrie Ionique et Moléculaire
Groupe des Ions Multichargés
LIMBE at Ganil
Nanogan at Lyon ( soon Nanogan3)

2. Questions
1. What is the excitation mechanism in ion-cluster collisions?
2 What is the dependance of fragmentation scheme versus the excitation energy?

3. OUTLINE Excitation and Capture
Fragmentation channels versus the charge state of C60
Experimental set up
Fragmentation for three time scales
- extraction (few hundred ns)
- tube( 20 µs)
-Trap (up to 1 second)
Lifetime measurements of C60q+
Conclusion

4. Excitation HCI ---> C60 HCI or A+ b << Ro
Large impact parameter
The same as in ion-atom collision
HCI or A+
b << Ro
Electronic and nuclear energies losses

5. How can a hot C60 lose excitation energy ?
Evaporation of dimere C2
Asymetrical fission (C2+, C4+…)
Multi-fragmentation (C13+, C15+)

6. Evaporation - Fission - Multifragmentation
as a fonction of the initial charge of the C60 in the 300 ns time scale
Xe30+ + C Xe(q-s)+ + C60r+ + n e- 1 2 3 4 5 6 7 8 9 10
1E-3
0.01
0.1
Stable
Multi-fragmentation
Probabilities
Fission
Evaporation
0.001
Initial charge states of C60

7. r = n + s Experimental set-up r C60 electrons s n Multi-anode
Micro-channel plates r
IONS
ECR Source
Cone Trap
Channeltron
cylindrical Analyser s
Time of flight tube
C60
Oven : T=500 °C
electrons
r = n + s
Si Detector (PIPS) n

8. TOF 1 TOF 2 Mass gate Ring Cone 1 Cone 2 Extraction zone
Acceleration, focusing
and steering plates
Cone 1
Cone 2

9. Variation of the trapping time40 30
Trapping time (µs) 20 10 30 40 50
1 oscil.
2 oscil.
3 oscil.
4 oscil.
5 oscil.
Time of flight (µs)

10. Fragmentation inside Fragmentation time Extraction 300 ns Tube 20 µs
acceleration
MCP detector
Time of flight Tube
Extraction
300 ns
A few oscillations
Mass gate
Tube
20 µs C 3+
selected 60
Mass gate
trapped up to 1s
second
Trap C 3+
selected 60

11. Recoil ions spectra : fragmentation inside the extraction region

12. Fragmentation of C604+ inside the tube
Selection of C604+ using the mass gate (v = v )
C584+
C604+
1 oscil.
2 oscil.
3 oscil.
4 oscil.
5 oscil.
C604+
C584+
TOF of trapped ions

13. Lifetime C603+ inside the trap
 =0.58 second
1 second

14. .3 s
1.52 s
0.9 s

15. Lifetime of C60r+ versus r and s values
1800
1600
s=1
1400
s=2
1200
1000
Lifetime (ms)
800
600
400
200 1 2 3 4 5 6
Charge state of C60

16. Statistical model RRK
Excitation energy-----> redistributed over all vibrationnel modes
Fragmentation rate
Prob = Number of cases ( at least one mode (E >Dissociation energy))/ Total Number of cases s
Large energy distribution ms µs

17. Comparison experiment theory for C603+
Probability
Stable
Gaussian energy distrabution
ext
trap
tube 20 40 60 80
100
120
140
160
E(eV)
E= 45 eV
∆E =73 eV
Fragmentation Ratio
0,0E+00
2,0E-03
4,0E-03
6,0E-03
8,0E-03
1,0E-02
1,2E-02
1,4E-02 20 40 60 80
100
120
140
160
E(eV)
P1(EXT)
P2(TUB)
P3(TRAP)
P3(Stable)
trap
Stable
tube
ext

18. Study of two successive fragmentation processes:
Future experiments
Study of two successive fragmentation processes:
Selected the C584+ (first fragmentation in the extraction)
the excitation energy can be estimated
Second fragmentation in the tube with a well know energy
Stability of high charge state of C60 (up to 9)
Lifetime measurements with metallic clusters

19. Conic Electrode Trap TOF 2 Cone 2 Ring Cone 1 TOF 1
Acceleration, focusing
and steering plates
TOF 1
TOF 2
Cone 1
Cone 2
Ring
Extraction zone

20. Operation of the trap : Timing diagram
Ion arrival in center
of trap
Projectile signal
0.9 µs
Projectile signal
Delayed e- signal
Cone 1
closing
0 V
200 V
Delayed projectile signal
Cone 2 closing
25 µs for C60+
13 µs for C604+
0 V
200 V
Collision t0
Cone 2
opening
Ion signal
+ few µs
e- signal
<< 1µs
time
Trapping time few µs to 1s
If correct e- signal in coincidence,
operation of the trap
Cone 2
Cone 1

21. Broad regime : Sharp turning points
Preliminary tests : Stability of trajectories
Critical regime or
Narrow regime
Broad regime
Efficiency
Cone voltage (V)
2 Types of trajectoires :
Narrow regime : Smooth turning points
Broad regime : Sharp turning points

22. Preliminary results : electron capture on Ar
Ar8+ + Ar Ar7+ + Ar+
Ar8+ + Ar Ar7+ + Ar3++ 2e-
Counts
t = 28 ms
Trapping Time (ms)
Trapping Time (ms)
t1 = 14 ms
t2 = 31 ms
t3 = 33 ms

23. Variation of the trapping time: Principe
Ar8+ + C60 Ar7+ + C602++ e-
Broad regime : Vc = 700 V

24. mbar
C603+
counts
Time (µs)
Probability(µs-1)
Pressure(mbar)