Barium-137m Half Life

Introduction

The purpose of the experiment was to conclude the half-life of Barium-137m. Half-lives are the time required for half of the remaining radioisotope to decompose into another element or becoming stable by releasing gamma-rays. Half-lives happen when an element is excited or in a meta-state (gamma), has too many neutrons (beta negative) or protons (beta positive), or has too many nucleons (alpha). To determine the half-life, arrange the formula of the number of half-lives that have elapsed to make the half-life the subject in the equation.

n=T/(t)1/2 → (t)1/2=T/n

where n is the number of half-lives that elapsed, T is the amount of time the radioisotope has decayed and (t)1/2 is the half-life of the nuclei, this is to determine the half-life of the radioisotope.

Barium-137m releases gamma rays, therefore, the nuclear decay equation will be

Barium-137m → Barium-137 + (Y)

Where (Y) will have no charge or mass.

The radiation emitted is gamma and has ionize radiation

properties, this is when atoms have so much energy that electrons become free, becoming positive ions. A Geiger-counter works when radiation interacts with the gas in the tube forming positive ions by ionization, the electrons are then attracted to the positive charge anode (inner conductor) with the atoms going towards the walls of the tube. The electrons then travel through wires making the electrical circuit and recombine with an ion, this is used to measure the quantity of radioactive particles that interact with it.

Purpose

The experiment was to conclude the half-life of barium-137m by using a Geiger counter.

Equipment.

Geiger-Muller tube and counter.
Eluting solution.
Cs-Ba mini generator.
Safety glasses.
Lab coat.
Planchet.
Stopwatch.
Safety gloves.

Safety

When performing the experiment, at all times wear gloves and a lab coat, treat the substance with care as to not drop it otherwise it may affect the result. Once finished, leave the planchet on the sample holder and leave it for the instructor

Method

When the equipment has been set up, turn on the Geiger counter without the radioactive substance near it and for one-minute record the background radiation, recording twice and using the average would yield a more accurate result. When finished, acquire the radioactive substance and place it on top of a planchet placing it near the Geiger counter tube and start recording, *record from the Geiger counter for 10 seconds * and then momentarily stop for 20 seconds before repeating. Once finished, place all the equipment to the designated area placed by the instructor. With the recordings, finalize the data by taking counts per 10 seconds to Counts Per Minute (CPM) and then subtract the average radiation background from the radioisotope.

Results and calculations

Discussion.

As displayed above, the time for the experimental half-life is approximately 160s, according to Pasco.com and the University of Tennessee the half-life of barium - 137m 156s or 153s respectively.

This margin of error could have been a result of not immediately recording when the radioactive substance was placed onto the planchet and restarting the recording multiple times. Basic steps of procedure could have avoided this as there were missing instruction sheets within the group. However, the graph was only approximating the half-life and does not perfectly indicate the time of the half life, but according to results the amount of Bq suddenly increases or decreases, this could be due to either the amounts of background radiation being interacted with the tube, or not stopping the recording in perfect sequence or perhaps both. This could have been prevented if there were less background radiation by providing larger spaces and if the recordings were timed accurately by being operated by

AIs.