The main isotope of Ti has mass 48 amu …so mass C 32 ~ Ti@C 28

1. The main isotope of Ti has mass 48 amu …so mass C32 ~ Ti@C28

2. Pulsed carbon cluster beam focused into the mass spectro-meter laser fires

3. Rings to fullerene region C27 C23 FT-ICR-MS of Titanium Carbon Clusters

4. C32 Ti@C28 C27 C23 FT-ICR-MS of Titanium Carbon Clusters

5. Ti@C28 C32 FT-ICR-MS of Titanium Carbon Clusters

6. Ti@C28 Ti@Cn

7. Cn Ti@C28 Ti@Cn

8. Cn Ti@C28 Ti@Cn no C28

9. C44 Ti@C44 C28 Cn Ti@C28

11. When the laser which is focused on the carbon rod fires the expanding plasma is skimmed into a narrow beam which passes into the next chamber

12. Ti@C28 Subtracting the lines for C32 experimental simulated Ti@C28

13. Ti@C44 Ti@C28

14. Laser vapourisation supersonic nozzle with a rotating translating rod source Paul Dunk Alan Marshall MagLab

15. with Paul Dunk and Alan Marshall

16. with Paul Dunk and Alan Marshall

17. Further pumping with Paul Dunk and Alan Marshall

18. with Paul Dunk and Alan Marshall

19. Ti@C28 experimental simulated Ti@C28

20. Clusters were formed by the laser ablation of a translating, rotating rod in He. The laser (532 nm 5-25 mj/pulse; 5-7 nanosec; approx 2-3mm diameter) was fired once in conjunction with a single pulse of He (800 μs width). The positive ions generated (without further ionization) proceeded through a supersonic expansion after exiting the rod holder and clustering region, then transferred to an accumulation octopole and He is pulsed in (10-3 torr approx)to thermalize the clusters. Up to ten laser shots are accumulated before the ions are transferred to the ICR cell for detection. Multiple time domain acquisitions (1-50) are co-added for each experiment. It should be noted that the skimmer is often removed, we are not critically pressure limited by the source. For collision induced dissociation experiments - after the ions are trapped in the ICR cell, a particular m/z species is mass selected (SWIFT, see below). The ions are then subjected to collisions with neutrals (Ar or He) while exciting them (SORI, see below). After the pulse of the collision gas into the ICR cell, there is a 25 second pump-down delay to reestablish base pressure in the ICR cell (10-10 torr) before excitation and detection of the ions.

21. Clusters were formed by the laser ablation of a translating, rotating rod in He. The laser (532 nm 5-25 mj/pulse; 5-7 nanosec; approx 2-3mm diameter) was fired once in conjunction with a single pulse of He (800 μs width). The positive ions generated (without further ionization) proceeded through a supersonic expansion after exiting the rod holder and clustering region, then transferred to an accumulation octopole and He is pulsed in (10-3 torr approx)to thermalize the clusters. Up to ten laser shots are accumulated before the ions are transferred to the ICR cell for detection. Multiple time domain acquisitions (1-50) are co-added for each experiment. It should be noted that the skimmer is often removed, we are not critically pressure limited by the source. For collision induced dissociation experiments - after the ions are trapped in the ICR cell, a particular m/z species is mass selected (SWIFT, see below). The ions are then subjected to collisions with neutrals (Ar or He) while exciting them (SORI, see below). After the pulse of the collision gas into the ICR cell, there is a 25 second pump-down delay to reestablish base pressure in the ICR cell (10-10 torr) before excitation and detection of the ions.

22. C30 Expanded view of C30 and possible Ti@C26 Ti@C26 noise

23. Ti@C28 C32

24. C32 After fragmentation of Ti@C30 and C34 with helium by SORI (CID) 382 383 384 385 386 387 m/z Ti@C30 & C34 Ti2C4 + H2O Ti@C28 Ti2C4 noise

25. C34 Ti@C30

26. Fragmetation of Ti@C28 • When Ti@C28 was isolated and subjected to CID (just like in the above case with Ti@C30), no fragmentation to Ti@C26 was observed. Most of the Ti@C28 remained intact illustrating the endohedral nature of the fullerene cluster and stability \. • Furthermore, Ti@C28 did not react with the small backgrond of oxygen and hydrogen during pulse of He. Agrees with the fullerene structure and that the titanium atom is located endohedrally. • An exohedrally bound metal is extremely easy to remove from the outside of the cage. The fragmentation behavior of Ti@C28 agrees with an endohedral fullerene species(as most Ti@C28 remained after collision with He).

27. Notes • All previous experiments(Ti doped rod .8%, lower and higher pressure) give fullerene C60 as the most dominant cluster formed. So these are conditions that likely apply to bulk production. • In bulk production experiments (carbon arc), the titanium fullerenes were found to be produced in the highest quantity relative to Hf and Zrendos (Shinohara et al.). It’s great to see that Ti@C28 has the highest apparent stability out of the group IV metals. Again, good news for possibility for bulk production of C28 materials. • Hf@C28 and Zr@C28 were also clearly observed to form…although in the same special abundance as Ti@C28 in the M@Cn series. • C28 has been long sought as it has been thought the smallest stable fullerene(C26 has also been thought to be stable enough to observe as well but much more interest in C28 due its predicted stability). • The small fullerenes could have major implications to fullerene growth mechanism. • Difficulty in fragmenting Ti@Cn(although C2 fragmentation provide compelling evidence for fullerenes) supports the most Ti@Cn occur as a result from growth rather than only fragmentation of larger fullerenes.

28. Current Experiments(a few of them!) • Group II, Group III and lanthanoids – to see if C28 is really stabilized by the donation of four electrons (ie tetravalent metals) to give M4+@C284- species. Calculations on C26 and C28 to probe structure and stability. • M4+@C284- is closed shell with large HOMO-LUMO gap and could be highly aromatic(based on “spherical aromaticy” rule) • Significance of Ti@C26, Ti@C28, etc to fullerene growth mechanism. • Ti@Cn will be formed from a pellet composed of carbon from two sources…half from high purity graphite and half from amorphous isotopically pure 13C with .8% Ti. This could conclusively answer the question as to whether a “top down” or “bottom up” growth mechanism occurs. • Endohedral growth mechism has never been probed before.(although most likely similar to empty cage)