Importance of Gamow-Teller Transitions in Nuclear Astrophysics

Gamow-Teller transitions play a crucial role in understanding the nuclear structure and excited states within nuclei. These transitions, along with Fermi transitions, provide valuable insights into beta decay processes, weak interactions, and isospin interactions in nuclei. By studying the selection rules, transition strengths, and decay modes associated with Gamow-Teller and Fermi transitions, researchers can uncover key information about nuclear astrophysics. Additionally, beta decay studies and charge exchange reactions provide further avenues for exploring and identifying transition strengths and states within nuclei, offering unique advantages in studying highly excited nuclear states.

• Gamow-Teller
• Nuclear Astrophysics
• Beta Decay
• Weak Interaction
• Charge Exchange

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1. http://tbn0.google.com/images?q=tbn:C31gybahhRBZBM:http://www.istanbul.edu.tr/edebiyat/edebiyat/dekanlik/dergi/cd/Archives/number_15/istanbul_universitesi_%2520logo.bmphttp://tbn0.google.com/images?q=tbn:C31gybahhRBZBM:http://www.istanbul.edu.tr/edebiyat/edebiyat/dekanlik/dergi/cd/Archives/number_15/istanbul_universitesi_%2520logo.bmp http://tbn0.google.com/images?q=tbn:dklIX7Q7RhbNOM:http://www.fbe.istanbul.edu.tr/V2/images/iu_fbe_logo.jpg GAMOW-TELLER TRANSITIONS IN THE 46Ti(3He,t)46V REACTION Merve DO AN stanbul University 1

2. Contents Contents - Beta Decay -Charge Exchange Reactions Isospin Structure RCNP-Grand Raiden Spectrometer Extraction of B(GT) Values 46V Importance of Gamow-Teller and Fermi Transitions Gamow-Teller and Fermi Selection Rules Measurement of B(GT) Transition Strengths 2

3. IMPORTANCE of GAMOW-TELLER and FERMI TRANSITIONS Gamow Teller transition is one of the allowed transition which is observed in beta decay. It is the most common ( ) type of weak interaction in nuclei. It gives information about excited states and nuclear structure of the core It is a key process in the Nuclear Astrophysics field. Fermi transition is an allowed transition in beta decay too. isospin ( ) type interaction in nuclei. only one transition to a state( sobaric Analog State) 3

4. GAMOW GAMOW- -TELLER TELLER and and FERMI SELECTION RULES FERMI SELECTION RULES Decay Mode Transition Spin Angular Parity Isospin Momentum l Operator s T F l = 0 T = 1 S = 0 = 0 GT | S| = 0,1 l = 0 = 0 | T| = 0,1 : spin operator : isospin operator 4

5. GAMOW-TELLER AND FERMI TRANSITION STRENGTHS sospin-flip Spin-flip 5

6. BETA DECAY Beta Decay Studies; ADVANTAGE!!! - Direct information of B(GT) values can be obtain from decay experiments. -Weak interaction process - Beta decay studies are limited in the low excitation energy regions. Absolute B(GT) values 6

7. CHARGE EXCHANGE REACTIONS In order to study the GT transitions to the states inaccessible by beta decay, (p,n) type charge exchange reactions was performed at intermediate energies (100-500 MeV/u) in 1980s. Extensive information was obtained about Gamow- Teller transition strengths. Because of the insufficent enrgy resolution (~ 300 keV) each peak could not be studied in detail. By adding different techniques , in RCNP/Osaka,(3He,t) type charge exchange reactions was performed and better energy resolution was achieved. (~30 keV) It was not possible to determine GT states in (p,n) reactions. ADVANTAGE!!! Highly excited states can be accesed 7

8. Y. Fujita et al., EPJA 13 (02) H. Fujita et al., PRC75 ( 07) 034310 J. Rapaport et al. NPA ( 83) 8

9. Under the assumption of isospin symmetry, beta decay and charge exchange reactions in mirror nuclei complemet each other. GT transition strengths can be anaylsed by combining beta decay and charge exchange reactions under this mirror symmetry process. 9

10. Isospin Structure B(GT) values are almost the same! 10

11. MEASUREMENT OF GAMOW-TELLER TRANSITION STRENGTHS Gamow-Teller transition strengths can be obtained when a absolute B(GT) value deduced in beta decay. Since we know the total half life of decay and branching ratios them we can find half life of individual states and accordingly to this absolute B(GT) values can be found as well. Here is a proportion between the measured cross section and B(GT) values at intermediate energies ( 100 MeV/u) and at 0 ; 11

12. RCNP 12

13. EXTRACTION of B(GT) VALUES Super Allowed Fermi Transition 0+ 0+ 13

14. EXTRACTION of B(GT) VALUES B(F)=N-Z GT- , F peak counts 7.7 0.9 14

15. RESULTS 15

16. COUNT 16 ENERGY

17. COUNT ENERGY(MeV) 17

18. SUMMARY The GT transition is usually measured in a beta decay, in which this transition is allowed. High excitation energies can be studied which are enable to study with beta decay. Isospin symmetry is a useful tool to study GT transition strengths because it provide us to combine charge exchange and beta decay. Excitation energies up to 12 MeV has been studied for the first time To add new informations to the literature, this study will be useful tool for the next studies. 18

19. SPECIAL THANKS TO ASSOC. PROF. ELA GAN O LU PROF. YOSHITAKA FUJITA DR. HIROHIKO FUJITA PROF. BAK AKKU PROF. YE M KTEM 19