1. Catalin Borcea IFIN-HH INPC 2019, Glasgow, United Kingdom
High energy α particle emission as a challenging method for synthesis of very heavy nuclei
Catalin Borcea
IFIN-HH
INPC 2019, Glasgow, United Kingdom
C. Borcea, IFIN-HH, INPC 2019

2. Outline Super-Heavy Elements (SHE): The status
Spectra of light particle emission in heavy-ion induced reactions at incident energy <10 MeV/A: implications for the SHE research
Necessary developments of the experimental methods
Conclusions
C. Borcea, IFIN-HH, INPC 2019

3. S. Hofmann et al., Eur. Phys. J. A 52 (2016) 180
SHE: The status
Z=113, 114, 115,116,117,118,…120?
S. Hofmann et al., Eur. Phys. J. A 52 (2016) 180
C. Borcea, IFIN-HH, INPC 2019

4. The limitations:
The use of 48Ca as primary beam (doubly magic, large neutron excess, tightly packed, highest observed cross sections) practically exhausted its potential
Radioactive targets used: 240,242,244Pu, 243Am, 245,248Cm, 249Bk, 249Cf, 254Es, 257Fm will be very difficult
The available combinations lead mostly to neutron deficient nuclei (fusion-evaporation reactions)
Odd nuclei preferred (alpha emission hindrance)
Cross sections in the pb-fb region
C. Borcea, IFIN-HH, INPC 2019

5. The challenges: Use of neutron rich incident beams above 48Ca
Increased competition with the dominating quasi-fusion (QF)/fast fission(FF) processes
Get closer to the island of stability, precisely establishing its existence and position
Refine the experimental approaches to get a reliable identification of SF nuclei
C. Borcea, IFIN-HH, INPC 2019

6. C. Borcea et al., Nucl. Phys. A 351 (1981), 312-320
Spectra of light particle emission in heavy-ion induced reactions at incident energy <10 MeV/A: implications for the SHE research
40Ar + 232Th → 220 MeV
48Ca+238U → 282Ds + α @270 MeV
C. Borcea et al., Proceedings of the International Symposium on Exotic Nuclei
2016, Kazan, Rusia
C. Borcea et al., Nucl. Phys. A 351 (1981),
C. Borcea, IFIN-HH, INPC 2019

7. Keywords: Collinear (0◦) Two-body : A+B →C+D (masses, incident energy)
Kinematic limit (KL): zero residual excitation energy
Residual excitation energy controlled by α energy
No other reaction channel(s) possible close to KL
Incident energy slightly above the barrier
Targets: α emitters
Miscellaneous:
- p, n also emitted but with lower cross section
- Sharp forwardly focused angular distribution
C. Borcea, IFIN-HH, INPC 2019

8. Implications for SHE synthesis
As product complementary to α (two body reactions only)
Close to 0 excitation energy (E*), controllable by the recorded alpha energy
E* ~ 6 MeV→ 1n evaporation channel opens with substantially higher cross section
Access to more n-rich nuclei
Access to higher Z projectiles (to be measured)
C. Borcea, IFIN-HH, INPC 2019

9. Theoretical model? A real challenge! Previous attempts (VZ, VB)
Momentum transfer across the nucleus (analogy to the Newton’s pendulum)
Fast propagation of momentum (speed of sound in nuclear matter)
Extra push (higher incident energy than in F-E reactions but lower excitation energy)
C. Borcea, IFIN-HH, INPC 2019

10. New experimental developments
Proof of principle: aiming to produce a known nucleus using a “classical” approach-GFS and compare the cross section:
Measurement of the α particle spectra for different projectiles and incident energies around the coulomb barrier for optimizing the cross section at KL
Coincident measurements heavy residue- α particle will eliminate the necessity of having a link to the known isotope (unambiguous identification)
Mass measurements possible (preliminary!)
40Ca+232Th → 268Hs + α; T1/2H.R.=0.4 s
C. Borcea, IFIN-HH, INPC 2019

11. WHY NOT YET SEEN? The 48Ca+238U example:
Incident energy: FE: 240 MeV, alpha: 270 MeV
Compound excitation: 40 MeV (4-5n evap.)
Heavy residue after alpha emission: close to zero or controlled by alpha excitation energy
Much lower energy for heavy residue and a different mass (momentum conservation)
Large difference in velocity: close to 20% more for F-E and correspondingly for energy
C. Borcea, IFIN-HH, INPC 2019

12. Conclusions
The solution of forwardly emitted high energy α particle may open a new possibility for SHE synthesis that deserves to be tested. Possible use of beams above 48Ca.
This method could also be used to obtain information for the empty cases of elements above Z=100 (production, mass and decay properties) with the benefit of higher cross section
Allows access to more neutron rich nuclei
Improvements of the identification methods will be needed to allow α-heavy residue coincidences
C. Borcea, IFIN-HH, INPC 2019

13. Thank you!
C. Borcea, IFIN-HH, INPC 2019