Ciro Santilli (@cirosantilli) - New articles

Fermentation Updated 2025-07-16

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f-orbital Updated 2025-07-16

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Multisig Updated 2025-07-16

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en.bitcoin.it/wiki/Multi-signature

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Term symbol Updated 2025-07-16

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This notation is so confusing! People often don't manage to explain the intuition behind it, why this is an useful notation. When you see Indian university entry exam level memorization classes about this, it makes you want to cry.

The key reason why term symbols matter are Hund's rules, which allow us to predict with some accuracy which electron configurations of those states has more energy than the other.

web.chem.ucsb.edu/~devries/chem218/Term%20symbols.pdf puts it well: electron configuration notation is not specific enough, as each such notation e.g. 1s2 2s2 2p2 contains several options of spins and z angular momentum. And those affect energy.

This is why those symbols are often used when talking about energy differences: they specify more precisely which levels you are talking about.

Basically, each term symbol appears to represent a group of possible electron configurations with a given quantum angular momentum.

We first fix the energy level by saying at which orbital each electron can be (hyperfine structure is ignored). It doesn't even have to be the ground state: we can make some electrons excited at will.

The best thing to learn this is likely to draw out all the possible configurations explicitly, and then understand what is the term symbol for each possible configuration, see e.g. term symbols for carbon ground state.

It also confusing how uppercase letters S, P and D are used, when they do not refer to orbitals s, p and d, but rather to states which have the same angular momentum as individual electrons in those states.

It is also very confusing how extremelly close it looks to spectroscopic notation!

The form of the term symbol is:

^{2 S + 1} L_{J}

(1)

The

2 S + 1

can be understood directly as the degeneracy, how many configurations we have in that state.

Video 1.

Atomic Term Symbols by TMP Chem (2015)

Source.

Video 2.

Atomic Term Symbols by T. Daniel Crawford (2016)

Source.

youtu.be/DAgEmLWpYjs?t=2675 term symbols for carbon ground state

Bibliography:

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x86 custom instructions Updated 2025-07-16

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Intel is known to have created customized chips for very large clients.

This is mentioned e.g. at: www.theregister.com/2021/03/23/google_to_build_server_socs/

Intel is known to do custom-ish cuts of Xeons for big customers.

Those chips are then used only in large scale server deployments of those very large clients. Google is one of them most likely, given their penchant for Google custom hardware.

TODO better sources.

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ASCII art Updated 2025-07-16

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It should be a crime to automatically generate ASCII art from images.

For some ASCII art in the Bitcoin blockchain see: ASCII art.

Random fun mentions:

en.wiktionary.org/wiki/roflcopter | knowyourmeme.com/memes/roflcopter
www.ludd.ltu.se/~vk/pics/ascii/junkyard/misc/who's_who.txt "Who's who in the ascii art world" contains a list of well known artists with their signatures

        z

        ^
        |    *------*
        |   /|      /
        |  / |     /|
top -------*------* |
        |  | *----|-*
        |  |/     | /
        |  |      |/
bottom ----*------*
        |  |      |
        +--|------|-----> y
       /   |      |
      /    |      |
  x  /     |      |
    v
          left   right

Code 1.

3D cube plot ASCII art by Ciro Santilli (2021)

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Astronomical unit Updated 2025-07-16

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Bicycle maintenance Updated 2025-07-16

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Bicycle vocabulary Updated 2025-07-16

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Ciro Santilli's hardware / Park Tool FR-5.2 Cassette Lockring Tool Updated 2025-07-16

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www.parktool.com/product/cassette-lockring-tool-fr-5-2