[realdon]

What is the ratio of M and M+2 ions in the mass spectrometry of a tetra chlorinated dioxin.
The intensities of the isotopic species can be found by applying the following formula: (a+b)^n, where a is the relative abundance of the light isotope, b is the relative abundance of the heavy isotope, and n is the number of chlorine atoms present.

Cl-35 75.77%, Cl-37 24.23%

This is the question but I don't know what a and b really stands for. Can someone help me in explaining the formula in the question?

Also, can you solve this by just multiplying the percentages together? like the molecule with 4 Cl-35 would be (.7577^4)? and the molecule with 3 Cl-35 and 1 Cl-37 would be 4(.7577^3)(.2423)?

Thanks a lot

[AWK]

Calibrate abundances to ³⁵Cl before using this formula. Then the formula is:
(1 + 0.3198)^4
The peak from 4 x ³⁵Cl will have an intesity = 1.

Compare your calculation with:
http://www.webelements.com/nexus/node/1225

[realdon]

Srry I still don't get what do you do after the calibration

so, since (1+ 0.3198)^4, a=1 and b=0.3198
but how do you calculate the intensity if there are 4 Cl-35, if there are 3 Cl-35 and 1 Cl-37
et cetera?