nuclear physics decay question
I am trying to find out why does
80 m Bromine
decay both beta negative and positron??
R & D, -
Materials Research Institute, Canada, Joined Nov 1998, 1252
Re: nuclear physics decay question In Reply to jamie at 14:29 Mar-22-2009 (Opening).
radio-chemistry, an interesting topic and what got me interested in NDT 35 years ago. But the isotope you refer to is not one usually associated with NDT!
Some background for those not familiar;
Bromine has 2 stable isotopes, Br79 and Br81.
Br80 is one of several unstable isotopes of Bromine.
Also, Bromine 80 is a nuclear isomer. A nuclear isomer has the same nuclear mass and same atomic number but different radioactive properties. In this case the isomers are 35Br80 and 35Br80m (where 35 is the Z number or atomic number and 80 the atomic mass and 35 would be a subscript and 80 and the letter m are superscript).
Wikipedia describes nuclear isomers as
a metastable state of an atomic nucleus caused by the excitation of one or more of its nucleons. A nuclear isomer occupies a higher energy state than the corresponding non-excited nucleus, called the ground state. Eventually, the nuclear isomer will release the extra energy and decay into the ground state,
In my old school text Radio and Nuclear Chemistry by Friedlander Kennedy and Miller (Wiley 1964) they note that the unstable isotope of Br80 decays by several decay methods including Beta negative with associated gamma emission, Beta positive (positron), and Electron Capture, and it has a short half-life of only 17.6 minutes.
Bromine 80m on the other hand has a half-life of 4.5 hours making it metastable. It decays by Isomeric Transition (IT) via internal-coversion electrons.
Since my reference was quite old I decided to check other locations available online and confirmed that the 80m mode was indeed the metastable version and did not decay by beta negative or beta positive modes. Instead it is the less stable version with a 17.6minute half-life that decays with the beta negative or beta positive modes.
You asked WHY Bromine80 decays with 2 options; i.e. both beta negative and positron (beta positive). Generally it is considered that beta negative decay dominates on the neutron excess side of the mass-parabola and positron decay on the proton rich side of the stable isobar. The actual route of decay is related to a variety of selection rules in quantum mechanics. There are allowed and forbidden transitions to de-excite to a more stable state. However, forbidden does not mean it is in fact not allowed, but instead exists with only a low probability.
Details of the classroom lectures on quantum mechanics describing the transitions are now too long ago in my past. I suggest you get a copy of Friedlander or some similar text to fill in the details (they are not trivial).
NOVO Armor 15 & NOVO Armor 22
The Armor Kit Contains the NOVO Armor, which provides additional mechanical protection to the NOVO 1
5WN & NOVO 22WN Detectors, the Armor Stand and a traveling soft cover.
- Newest shock absorbent technology case
- Water resistant design
- Supports wired & wireless communication
- Multiple positioning options
- Tripod connection using the Built-in 1/4” threads
- Simple Detector battery replacement
M2M PANTHER is a phased-array equipment designed for both desktop and industrial applications, offer
ing unparalleled performance in a compact unit. It combines the speed required for industrial integrated Phased-Array Ultrasound (PAUT) solutions, with the most complete set of total focusing method (TFM) imaging techniques, making it the ultimate tool for R&D and procedure qualification.
NEW Wheel Type Phased Array Probe
DOPPLER NEW Wheel Type Phased Array Probe, more stable, new tyre
makes lesser acoustic attenuation
, much lighter makes easier to handle,
more slim size, magnetic and mechanical encoder optional etc...more
NEW! The PragmaPro Instrument Platform
The PragmaPro is based on a modular cartridge technology and supports various NDT
ities such as UT, PAUT, ECT and many more. This new platform is
based on a machined, powder-coated aluminum frame for shock-proofness, best sealing
qualities and maximum heat dissipation. This is practical to extend the outdoor
temperature range and/or to extend the power injected in the transducers. The
PragmaPro is aiming at a very wide range of applications, such as weld scanning,
corrosion mapping and composite testing.