Presentation on theme: "Survival of Excited Compound Nuclei and Online Chemistry Experiments at Texas A&M University C. M. Folden III Cyclotron Institute, Texas A&M University."— Presentation transcript:
Survival of Excited Compound Nuclei and Online Chemistry Experiments at Texas A&M University C. M. Folden III Cyclotron Institute, Texas A&M University June 12, 2014
We are interested in both the chemistry and physics of heavy elements. Nuclear Reactions: Understand fusion-evaporation reactions leading to the production of heavy elements. Understand the survival of excited compound nuclei. Chemistry: Perform “online” experiments with activity collected from a physical pre-separator. Use “designer” molecules to study the complexation behavior of transactinides and their homologs.
MOTIVATION: Prospects of SHE Synthesis with Z p > 20 Rxns. Studied: 48 Ca CN 45 Sc CN 50 Ti CN 54 Cr CN
The evaporation residue cross section can be described as: Fission
Do Taylor Series expansions around E = E* – B n and E = E* – B f, and use d(ln /dE 1/T: This relationship is approximately true, but determining the input values is not trivial.
The 48 Ca-induced reactions show the influence of B f – B n on survival and therefore cross section. The significant change in B f – B n for Z > 20 is problematic.
Our focus has been on determining which projectile is most likely to lead to the next new element. Substantially reduced cross sections are observed for 45 Sc and 50 Ti compared to 48 Ca. The data suggest that produced elements will be very difficult (cross sections ~ fb are reasonable).
Making heavy atoms available for online chemistry requires several steps. Rotating Degrader Cyclotron Gas StoppingChemistry Experiment Physical Pre-Separation
STAR-CCM+ and SIMION were used for simulations. V window – V nozzle = 420 V Lines are 10 V apart Nozzle: 2.0 L/min AC Inlet: 0.5 L/min
Two modes of operation: fast extraction (<150 ms) or maximum efficiency (several seconds for extraction). Results suggest that online chemistry experiments are be feasible. An online laboratory is being installed. Next step: Aerosol transportation measurements. Extraction Efficiency for 118 Sn( 40 Ar, 6n) 152 Er New Gas Stopper at the MARS Focal Plane Recoil Transfer Chamber Schematic
Nuclear Reactions: Study reactions with lower cross sections such as 48 Ca, 45 Sc, 50 Ti, 54 Cr Ta, 197 Au, etc. Products will be deformed and weakly shell-stabilized. Provides a complement to the current studies. Long term: Move toward light transactinide production (Z ~ ). Offline Chemistry: Start studying extraction of group 13 elements. Online Chemistry: Begin “manual” chemistry experiments and switch to “automated” experiments. Using cryptands or crown ethers as extractants.
Crown ethers have shown promise for separation of Group 4 elements. Good separation factors. High extraction: (K d ~ 10). Fast extraction. Courtesy of R. Sudowe. DC18C6
13 LLNL is developing automated systems for atom-at-a-time chemistry Product transport from cyclotron Gas-Liquid Interface for Transferring Transactinides to Automated Radiochemistry (GLITTAR) Removes reaction products from transport gas and transfers them to aqueous phase Super Heavy Element Liquid Automation (SHELA) Modular, rapid chemistry system for low volume separations Macrocyclic ligands for specific ion extraction Slide courtesy of D. A. Shaughnessy.
Acceptance cone: ±50 mrad horizontally and vertically Efficiency: 50-75% for 59 Co Bi → 267 Ds + n B max = 2.2 T m Arrived at Texas A&M in January 2014.
We have a broad program to study the chemical and physical properties of heavy elements. Current experiments have demonstrated that the production of new superheavy elements may be very difficult. We have a vibrant offline chemistry program and a new gas stopper to enable online experiments. We are leaders in a national collaboration to perform online chemistry experiments. A new gas-filled separator will substantially increase the sensitivity of all of our experiments. We are starting to receive national and international interest in our program.
Heavy Element Group Members: M. C. Alfonso M. E. Bennett T. K. Bhardwaj M. J. DeVanzo L. D. Fields M. M. Frey D. A. Mayorov E. E. Tereshatov (not pictured) T. A. Werke
N. Gharibyan R. A. Henderson K. J. Moody D. A. Shaughnessy Grant A-1710 J. Despotopulos J. Rolfes R. Sudowe M. E. Bennett J. P. Greene Funding agencies: