Mass Spectrometry Simulation for Atomic Abundances and Isotopes
1. Double click on the MATLab icon.
2. After the program opens, you will see a screen and the cursor will be positioned at a prompt that looks like this: >> Type clear and return.
3. Type load atom.dat; at the prompt. This loads a file which contains the atomic numbers, mass numbers, isotopic masses and isotopic abundances for elements 1-36.
4. Now type atno=atom(:,1); This pulls out all the atomic numbers. We will use this to select a particular atom.
5. Type mass=atom(:,3); to load the masses of each isotope and perc=atom(:,4); to load the percent abundances.
6. To select a particular element, type i = find(atno==#); but type a number between 1 and 36 instead of the number sign. For example, to see the spectrum for Magnesium, type i = find(atno==12); Elements of atomic numbers 17, 29, 30, 32, 34 and 35 should have interesting spectra, but you can try any between 1 and 36.
7. To plot the mass spec for an element, type the following: xleft=min(mass(i))-5; xrght=max(mass(i))+5; these 2 commands set the axis length bar(mass(i),perc(i)); the width of the bars is arbitrary. The position of the * at the bottom indicates the actual mass being plotted. axis([xleft xrght 0 100]); finishes the graph.
8. To get a cursor which will allow you to actually read values and print them out to the screen val=ginput(#) where # is the number of peaks on the graph. Position the cursor at the top of each bar, in line with the * and click. Continue until all peaks have been read.
9. To do another element, repeat steps 6 and 7. Do at least 3 elements.
10. Then, at the command prompt, type massspec. This will start a program which yields a better plot. All you need to enter is the atomic number and to type in the val=ginput(#) command. Do at least 5 elements with this.
Q: How does the atomic weight on the periodic table relate to the peaks observed?