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)

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

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

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

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

Evaporation - Fission - Multifragmentation as a fonction of the initial charge of the C60 in the 300 ns time scale Xe30+ + C60 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

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

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

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

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

Recoil ions spectra : fragmentation inside the extraction region

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

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

.3 s 1.52 s 0.9 s

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

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 60 80 100 s Large energy distribution ms µs

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

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

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

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

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

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

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

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