16 questions linked to/from Understanding group theory easily and quickly
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The ground-state term symbol from a $\mathrm{d^3}$ Tanabe-Sugano diagram is $\mathrm{^4F}$. My question is how the total orbital quantum number $\Lambda=3$, or $\mathrm{F}$ term, arises. For a $\... • 1,586 7 votes 1 answer 513 views ### Notation for excited states I am reading some papers about quantum chemistry and in one I found a notation for excited states of a molecule that I don't understand at all. In the picture below you can see the potential curves ... • 369 1 vote 1 answer 911 views ### How does a d4 high-spin complex have a spin-allowed transition without violating the selection rule for total angular momentum? 1) I am confused by the fact that the spin-allowed transition for a high-spin d4 complex is 5E→T2 Doesn't this violate the spin selection rule for total angular momentum? 2) Also, for a d6 complex, ... • 59 0 votes 1 answer 854 views ### How do I get irreducible representations? I'm currently trying to do a problem where it asks me to "show that the irreducible representations spanned by the atomic x-, y-, and z- coordinates is independent of the choice of local coordinate ... 5 votes 1 answer 269 views ### Is there a geometrically intuitive explanation of the equivalence of the numbers of irreducible representations and symmetry classes? In group theory, as used in chemistry, we’re familiar with the idea that the number of irreducible representations of a symmetry group equals the number of classes of symmetry operations, e.g. three ... • 213 1 vote 1 answer 316 views ### Spectroscopy pyrazine molecule Considering pyridazine and pyrazine molecules, I am asked to say if I can distinguish one from the other in a sample. I supposed that is possible because pyrazine belongs to D2h and so it has the ... 0 votes 1 answer 244 views ### Understanding molecule infrared absorption My chemistry course requires us to know which molecules absorb infrared, and under which vibrational modes that they do. My professor provides us the following rule, which is very confusing for me and ... 5 votes 1 answer 189 views ### How do I interpret characters that are not 1 or -1 in a point group table? When the character in a point group table is listed as 1 or -1, I understand how an object/orbital etc. transforms to give either itself or the negative of itself. When the character in a point ... 1 vote 0 answers 280 views ### What is a quick and easy way to find an alternative axis of symmetry? According to a question in my book (1​R,3​R)-1,3-dichloro-2,2-bis[(S)-chloro(2H1)methyl](1,3-2H2)propane has an S4 alternative axis symmetry. I tried trial-and-error method using an axis that passes ... • 597 2 votes 0 answers 243 views ### How is group theory (and matrices) used in symmetry operations? [closed] I am a high school IB student. For my 2-year math course, there is an internal assessment called "exploration" which should be max. 12 pages long. The goal of this assignment is for students to ... 2 votes 0 answers 183 views ### What does the order of a class mean in a character table? I am not from a chemistry background. I am trying to see how the symmetry operations affect the stiffness tensor which led me in the path of understanding character tables. I am looking at the ... • 21 2 votes 1 answer 138 views ### Projection Operator Method on Cl4+ I am not quite sure how to start on 1b.We are given 2 diagrams but I am not sure how to use the second one in the question, or if we have to. I got the point group for Cl4+ to be (D2h) however, but ... • 51 1 vote 1 answer 124 views ### How to distinguish two molecules with same formula but different geometry with vibrational spectroscopy There is a sample that we know is all made up by only one of these two molecule: how you can see they have the same formula but two different geometries. The question is if it is possible to know by ... • 193 2 votes 0 answers 95 views ### Are the$+\leftrightarrow+$and$-\leftrightarrow-\$ methanol rotational transitions dipole-allowed?

I am quite confused about the origin and justification of the rotational selection rules of methanol, and I would appreciate any help or references. As far as I understand, there are three irreducible ...