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  2. Molecular electronic transition - Wikipedia

    en.wikipedia.org/.../Molecular_electronic_transition

    This process is denoted as a σ → σ* transition. Likewise, promotion of an electron from a pi-bonding orbital (π) to an antibonding pi orbital (π*) is denoted as a π → π* transition. Auxochromes with free electron pairs (denoted as "n") have their own transitions, as do aromatic pi bond transitions.

  3. Hückel method - Wikipedia

    en.wikipedia.org/wiki/Hückel_method

    The method predicts how many energy levels exist for a given molecule, which levels are degenerate and it expresses the molecular orbital energies in terms of two parameters, called α, the energy of an electron in a 2p orbital, and β, the interaction energy between two 2p orbitals (the extent to which an electron is stabilized by allowing it ...

  4. List of formulae involving π - Wikipedia

    en.wikipedia.org/wiki/List_of_formulae_involving_π

    where C is the circumference of a circle, d is the diameter, and r is the radius.More generally, = where L and w are, respectively, the perimeter and the width of any curve of constant width.

  5. The digits of pi extend into infinity, and pi is itself an irrational number, meaning it can’t be truly represented by an integer fraction (the one we often learn in school, 22/7, is not very ...

  6. Bailey–Borwein–Plouffe formula - Wikipedia

    en.wikipedia.org/wiki/Bailey–Borwein–Plouffe...

    Using the P function mentioned above, the simplest known formula for π is for s = 1, but m > 1. Many now-discovered formulae are known for b as an exponent of 2 or 3 and m as an exponent of 2 or it some other factor-rich value, but where several of the terms of sequence A are zero. The discovery of these formulae involves a computer search for ...

  7. Machin-like formula - Wikipedia

    en.wikipedia.org/wiki/Machin-like_formula

    which he used to compute π to 100 decimal places. [1] [2] ... In Pi Day 2024, Matt Parker along with 400 volunteers used the following formula to hand calculate ...

  8. Selection rule - Wikipedia

    en.wikipedia.org/wiki/Selection_rule

    In quantum mechanics the basis for a spectroscopic selection rule is the value of the transition moment integral [1], =, where and are the wave functions of the two states, "state 1" and "state 2", involved in the transition, and μ is the transition moment operator.

  9. Frontier molecular orbital theory - Wikipedia

    en.wikipedia.org/wiki/Frontier_molecular_orbital...

    This means there is one 4q + 2 suprafacial system and no 4r antarafacial system; thus, the conrotatory process is thermally allowed by the Woodward–Hoffmann rules. The HOMO of the sigma bond (i.e., a constructive bond) and the LUMO of the pi bond are important in the FMO theory consideration.