# Presentation: 146434

## Decay studies of r-process nuclei

- Karl-Ludwig Kratz

-  Max-Planck-Institut für Chemie, Mainz,  Germany
-  Department of Physics, Univ. of Notre Dame,  USA

- T1/2

- Pn

- Sn

- n

****

- HRIBF 2006

## R-process observables

- scaled theoretical solar r-process

- scaled solar r-process

- Nb

- Zr

- Y

- Sr

- Mo

- Ru

- Rh

- Pd

- Ag

- Ba

- La

- Ce

- Pr

- Nd

- Sm

- Eu

- Gd

- Tb

- Dy

- Ho

- Er

- Tm

- Yb

- Lu

- Hf

- Os

- Ir

- Pt

- Au

- Pb

- Th

- U

- Ga

- Ge

- Cd

- Sn

**Elemental**** abundances in UMP halo stars**

**r-process observables**

**Solar system ****isotopic**** abundances, N****r,******

- “**FUN-anomalies”**** in meteoritic samples**

**isotopic**
**composition**
**   ****Ca, Ti, Cr,**
**   ****Zr, Mo, Ru,**
**   ****Nd, Sm, Dy**
**   ****    ↷ **
** ****r-enhanced**

**Historically,**
**nuclear astrophysics has always been **
**concerned with**
** ****interpretation of the **
**  ****origin of the chemical elements**
**  ****from astrophysical and cosmochemical **
**  ****observations **
** ****description in terms of specific**
**  ****nucleosynthesis processes**** **
**  ****(already B2FH, 1957).**

****** ****[‰]**

**ALLENDE INCLUSION**
**EK-1-4-1**

**Mass number**

- CS 22892-052 abundances

- T9=1.35; nn=1020 - 1028

**R-process observables**

- , Bi

## Nuclear-data needs for the classical r-process

**Nuclear-data needs for the classical r-process**

** ****nuclear masses**

- Sn-values        r-process path
- Q, Sn-values  theoretical -decay properties, n-capture rates

******-decay properties**

** ****neutron capture rates**

** ****fission modes**

- T1/2  r-process progenitor abundances, Nr,prog
- Pn     smoothing Nr,prog                 Nr,final (Nr,)

- RC +DC  smoothing Nr,prog during freeze-out

- SF, df, n- and -induced fission  “fission (re-) cycling”; r-chronometers

** ****nuclear structure development**

-  level systematics
-  “understanding” -decay properties
- - short-range extrapolation into unknown regions

## History and progress in measuring r-process nuclei

**History and progress in measuring ****r****-process nuclei**

**Definition:**         r-process isotopes lying **in** the process path at freeze-out
- 		 	 **↷** when r-process falls out of (n,)-(,n) equilibrium
- 	            even-neutron isotopes **↷** “waiting points”
- 			           important nuclear-physics property **T****1/2**
- 	            odd-neutron isotopes  **↷** connecting the waiting points
- 			           important nuclear-physics property **S****n**  ******n.******

- In **1986** a new r-process astrophysics era started:

- at the ISOL facilities **OSIRIS,**** ****TRISTAN and SC-ISOLDE**

- T1/2 of **N=50** “waiting-point” isotope **80****Zn****50** (top of A80 Nr, peak; “weak” r-process)

- T1/2 of **N=82** “waiting-point” isotope **130****Cd****82** (top of A130 Nr, peak; “main” r-process)

- In **2006, **altogether more than **50** r-process nuclei** **have been measured,
- 	which lie in the process path at freeze-out.

- These r-process isotopes range from **68****Fe** to **139****Sb**.

- The large majority of these exotic nuclei was identified at CERN/ISOLDE

- via the decay mode of
- 	             ******–****delayed neutron emission.**

## What we knew already in 1986 ...

**What we knew already in 1986 ...**

- K.-L. Kratz et al (Z. Physik A325; 1986)

- Exp. at old SC-ISOLDE
- 	with plasma ion-source
- 	       quartz transfer line
- 	and dn counting

- _Problems:_
- high background from
- 	-surface ionized 130In, 130Cs
- 	-molecular ions [40Ca90Br]+

- _Request:_ **SELECTIVITY !**

- Shell-model (QRPA; Nilsson/BCS) prediction

- 1.0

- T1/2(GT) = 0.3 s

**4.1**

- 1+

- 2.0

- g7/2, g9/2

- Q = 8.0 MeV

- 1+

- 1+

- 1+

- 1+

- 1+

- 1+

- 1+

- 0

- 1.0

- 3.0

- 4.0

- 5.0

- 6.0

- 1-

- IKMz – 155R(1986)

**T****1/2**** = 230 ms**

- T1/2 = (195 ± 35) ms

## The r-process “waiting-point“ nucleus 130Cd

**The r-process “waiting-point“ nucleus ****130****Cd**

- Q

- 7.0

- 8.9

- 2.9

- 2QP

- 4QP

- J=1+

- {g7/2, g9/2}

- Sn

- T1/2, Q, E(1+), I(1+), log ft

- 1.2

- ...obtain a physically consistent picture!

- “free choice” of combinations:

- low  E(1+) with low  Q
- high E(1+) with low  Q
- low  E(1+) with high Q
- high E(1+) with high Q

**T****1/2****(GT)**
**  ****233 ms**
**1130 ms**
**    ****76 ms**
**  ****246 ms**

- (log ft=4.1)

##  Request: Selectivity !

**Improvements since 1993 at**
**PS-Booster ISOLDE **

-  Fast UCx target
-  Neutron converter
-  Laser ion-source
-  Hyperfine splitting
-  Isobar separation
-  Repeller
-  Chemical separation
-  Multi-coincidence setup

-  Request: **Selectivity !**

- 50

- 800

- >105

- the **Ag** “**needle**” in the **Cs** “**haystack**”

**Why ?**

**How?**

##  Request: Selectivity !

-  Request: **Selectivity !**

**Laser ion-source (RILIS)**

- Chemically selective,
- three-step laser ionisation
- of Cd into continuum

- -singles spectrum

- Laser **ON**

- Laser **OFF**

- Comparison of
-     **Laser ON**
-            to
-     **Laser OFF**
-       spectra

- Properties of the laser system:
- Efficiency ≈ 10%
- Selectivity ≈ 103

- 5*s*2 1*S*0

- 5*s* 5*p* 1*P*1

- 5*s* 5*d* 1*D*2

- 510.6nm

- 643.8nm

- 228.8nm

**Cd**

## !

- Mass scan at HRS (ISOLDE) in 2002;
- efficiency corrected

**in reality, ****„on a good day...“**
******M/M ≈ 1/4000**

******M/M=7.5*10****-5**

- HRS design≥ 1/104

-  Request: **Selectivity !**

**Isobar separation**

**In**

**Cs**

**Cd**

**Cd 2.000**

**In 17.000**

- with HRS

##  Request: Selectivity !

-  Request: **Selectivity !**

**Chemistry  ** in the transfer line between target
-                                                   and ion-source  ↷  **thermochromatography**** **

- Deposition of Zn, Rb, Ag, In, Cd and Cs in a quartz tube with a temperature gradient
- 		 separation Cd, from Cs, In

- Prototype UCx target at
- CERN/ISOLDE with
**temperature-controlled**
**quartz transfer-line**
****** **Oct. 2005

**Diploma thesis C. Jost (2005)**

## Surprises

**Surprises**
** ****high [********g****7/2********g****9/2****] 1****+**** state**
** ****weakening of the ********g****7/2 ****- ********g****9/2**
**  ****residual interaction**
** ****high Q********-value**

**130****In****81**

**OXBASH**
**(B.A. Brown, Oct. 2003)**

- 0

**1****-**

- 473

**3****+**

*1382 (old)*

**1****+**

**1****+**

- 895

**0****-**

- 1441

**1****-**

- 1906

**1****-**

- 2515

- 2598

**1****-**

**0****-**

***2181 (new)***

**reduction of the TBME (1+) by 800 keV**

**Full spectroscopy ****130****Cd decay**

## Snapshots: r-process paths for different neutron densities 

-      42       44      46        48      **50**** **     52       54       56      58        60      62       64        66       68       70       72       74        76       78       80      **82**

- Fe

- Co

- Ni

- Cu

- Zn

- Ga

- Ge

- As

- Se

- Br

- Kr

- Rb

- Sr

- Y

- Zr

- Nb

- Mo

- Tc

- Ru

- Rh

- Pd

- Ag

- Cd

- In

- Sn

- Sb

- Te

- I

- Xe

- Cs

- Ba

**82**      84      86      88      90      92     94

**Snapshots: r-process paths for different neutron densities **

**heaviest isotopes with ****measured T****1/2**

**g****9/2**

**d****5/2**

**s****1/2**

**g****7/2**

**d****3/2**

**h****11/2**

**g****9/2**

**p****1/2**

**p****3/2**

**f****5/2**

**f****7/2**

## R-process path for nn=1020

-      42       44      46        48      **50**** **     52       54       56      58        60      62       64        66       68       70       72       74        76       78       80      **82**

- Fe

- Co

- Ni

- Cu

- Zn

- Ga

- Ge

- As

- Se

- Br

- Kr

- Rb

- Sr

- Y

- Zr

- Nb

- Mo

- Tc

- Ru

- Rh

- Pd

- Ag

- Cd

- In

- Sn

- Sb

- Te

- I

- Xe

- Cs

- Ba

**82**      84      86      88      90      92     94

**R-process path for n****n****=10****20**

- „waiting-point“ isotopes at nn=1020 freeze-out

## R-process paths for nn=1020 and 1023

-      42       44      46        48      **50**** **      52       54       56      58        60      62       64        66       68       70       72       74        76       78       80      **82**

- Fe

- Co

- Ni

- Cu

- Zn

- Ga

- Ge

- As

- Se

- Br

- Kr

- Rb

- Sr

- Y

- Zr

- Nb

- Mo

- Tc

- Ru

- Rh

- Pd

- Ag

- Cd

- In

- Sn

- Sb

- Te

- I

- Xe

- Cs

- Ba

**82**      84      86      88      90      92     94

- „waiting-point“ isotopes at nn=1023 freeze-out

**R-process paths for n****n****=10****20**** and 10****23**

- (T1/2 exp. : 28Ni – 31Ga, 36Kr, 37Rb,47Ag – 51Sb)

## R-process boulevard for nn=1020, 1023 and 1026

-      42       44      46        48      **50**** **      52       54       56      58        60      62       64        66       68       70       72       74        76       78       80      **82**

- Fe

- Co

- Ni

- Cu

- Zn

- Ga

- Ge

- As

- Se

- Br

- Kr

- Rb

- Sr

- Y

- Zr

- Nb

- Mo

- Tc

- Ru

- Rh

- Pd

- Ag

- Cd

- In

- Sn

- Sb

- Te

- I

- Xe

- Cs

- Ba

**82**      84      86      88      90      92     94

- (T1/2 exp. : 28Ni, 29Cu, 47Ag – 50Sn)

**R-process ****boulevard**** for n****n****=10****20****, 10****23 ****and 10****26**

- „waiting-point“ isotopes at nn=1026 freeze-out

## Astrophysical consequences

**... resulting from new experimental and theoretical ****nuclear structure**** information:**
** ****better understanding of ****shape**** of and ****matter flow****  through the major r-process **
**  ****bottle-neck at the A********130 N****r,******** peak**
** ****no justification to question ****waiting-point**** concept **
**  ****(Langanke et al., PRL 83, 199; Nucl. Phys. News 10, 2000)**
** ****no need to request sizeable effects from ********-induced reactions**** **
**  ****(Qian et al., PRC 55, 1997)**

**Astrophysical consequences**

****** ****r-process abundances**** in the Solar System and in UMP Halo stars...**
**	****	****	****	****                 ****...are governed by nuclear structure!**

**Nuclear masses from **
**AMDC, 2003**
**ETFSI-Q**
**Normalized to N****r,******** ****(****130****Te)**

**Longer T****1/2****!**

**„****short“ T****1/2**

**„****long“ T****1/2**

## Abundance clues and constraints

**Abundance clues and constraints**

- Observations versus calculations    - solar system
- 		                   - UMP halo stars

-      Conditions for „main“ and „weak“ r-process    - n-densities
-                                                                 - entropies

-      Split between the two r-processes    - 129I (Wasserburg et al.)
-                                                                 - below N=82

-      R-process chronometric pairs    - Th/Eu, Th/U
-                                                          - new: Th/Hf

-      Ages of UMP stars, Galaxy and Universe

-      Suggestions on r-process sites

-      Galactic chemical evolution

-      (Un-) importance of fission recycling

## Conclusion

**Conclusion**

- nuclear-physics data

- for explosive nucleosynthesis calculations
- 		    still **unsatisfactory !**

-  better **global** **models**

- for **all** nuclear shapes
- (spherical, prolate, oblate, triaxial, tetrahedral,...)

- and **all** nuclear types
- (even-even, odd-particle, odd-odd)

-  more **measurements**

- masses !
- gross -decay properties
- level systematics
- full spectroscopy of selected
-               **key“ waiting-point isotopes**

- Despite impressive experimental and theoretical progress,
- situation of

- with sufficiently **large** SP model space,