where expertise comes together - since 1996 -

The Largest Open Access Portal of Nondestructive Testing (NDT)

Conference Proceedings, Articles, News, Exhibition, Forum, Network and more

where expertise comes together
- since 1996 -
864 views
Technical Discussions
jamie
jamie
14:29 Mar-22-2009
nuclear physics decay question

I am trying to find out why does
80 m Bromine
35

decay both beta negative and positron??

 
 Reply 
 
Ed Ginzel
R & D, -
Materials Research Institute, Canada, Joined Nov 1998, 1286

Ed Ginzel

R & D, -
Materials Research Institute,
Canada,
Joined Nov 1998
1286
01:51 Mar-23-2009
Re: nuclear physics decay question
In Reply to jamie at 14:29 Mar-22-2009 (Opening).

Jamie…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).

 
 Reply 
 

Product Spotlight

NovaScope 6000

The all-digital Novascope 6000 is a portable, ultra-high precision thickness gauge for high-speed
...
thickness measurement. Novascope 6000 has unmatched capabilities and unique features including: •Superior Resolution with high contrast, high-speed color RF display •High pulser voltage •Real-time video output •Increased internal/external data storage •Programmable SetUp features •Battery & AC Powered
>

Aerospace Systems - Automated Ultrasonic Inspection

USL are specialists in the design and manufacture of turnkey ultrasonic inspection systems for aer
...
ospace applications. From monolithic composites to complex honeycomb structures. This video shows just a few examples of what is possible, find out more at: www.ultrasonic-sciences.co.uk
>

HD-CR 35 NDT Computed Radiography System

Portable high-resolution CR scanner for all radiography applications - weld testing, profile images
...
and aerospace. No matter what type of radiographic testing you are performing, the unique TreFoc Technology of the HD-CR 35 NDT imaging plate scanner always guarantees the highest image quality.
>

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
>

Share...
We use technical and analytics cookies to ensure that we will give you the best experience of our website - More Info
Accept
top
this is debug window