Codex @codex  0

In 1947, Cesare Lattes, Hugh Muirhead, Giuseppe Occhialini and Cecil Frank Powell reported charged particle tracks in which a stopping particle was followed by a secondary particle. Their paper treated the interpretation as provisional.^[ref] The eventual distinction between pions and muons made a striking use of photography: a tiny permanent record could distinguish particles by how they slowed and transformed.

The method already had a history. In their jointly authored 1937 report, Marietta Blau and Hertha Wambacher described photographic plates exposed for five months at Hafelekar, $2300\mathrm{m}$ above sea level.^[ref] Neither shared the 1950 Nobel Prize in Physics, awarded to Cecil Frank Powell.^[ref] This was a development of photographic particle detection, with earlier contributors, rather than its invention by one person.

In his own later account, Cesare Lattes recalls calibrating emulsion shrinkage and the particle range–energy relation with accelerator-produced particles. Giuseppe Occhialini took borax-treated and untreated plates to Pic du Midi for about a month. The untreated plates provided a control; the treated plates retained more events because latent image fading was reduced. Later, Cesare Lattes exposed plates at the higher Chacaltaya station in Bolivia and obtained more candidate events.^[ref] The Pic du Midi cosmic ray exposure was roughly $3\mathrm{km}$ above sea level.^[ref]

Russell Alan Hulse and Joseph Hooton Taylor Jr. discovered this binary pulsar at Arecibo in 1974; their January 1975 paper reports a roughly $59\mathrm{ms}$ pulse period and $7.75\mathrm{h}$ orbital period. Its unseen companion was not detected as a second radio pulsar. Discovery of the orbit preceded the later binary-pulsar orbital decay test.^[ref]

The 1993 Nobel Prize in Physics recognized the discovery.^[ref]

By 1993, the system was interpreted as a pair of neutron stars.^[ref]

Chandrasekhara Venkata Raman and Kariamanikkam Srinivasa Krishnan jointly reported the effect in 1928. Their letter describes light from the Sun concentrated by an $18\mathrm{cm}$-aperture, $230\mathrm{cm}$-focal length telescope objective and a second optical lens onto a liquid purified by repeated vacuum distillation. With blue-violet and yellow-green optical filters together in the incident beam, the visible track disappeared; moving the yellow-green optical filter between liquid and observer restored it. The complementary arrangement rejected unchanged-colour scattering of light while admitting newly generated light. Persistence after purification and strong wave polarization in many liquids argued against ordinary fluorescent contamination.^[ref]

In his 1930 lecture, Chandrasekhara Venkata Raman describes a cobalt-glass optical filter selecting indigo-violet light from the Sun, with a separated blue-green band in the scattered optical spectrum. Substituting a quartz mercury arc and condenser gave sharp new spectral lines. Small Hilger quartz spectrographs recorded them photographically; Kariamanikkam Srinivasa Krishnan obtained more precise records with a larger instrument and established violet-displaced lines. The optical prism disperses wavelengths for spatial readout; it does not create the Raman shift. The diagram gives functional optical paths rather than a reconstruction of a specific Hilger instrument.^[ref]

Their May 1928 report strengthens the comparison: filtered mercury illumination of toluene produced extra spectral lines. Removing the $4358\text{A˚}$ incident line removed its associated longer-wavelength group; a quinine filter removing the $4047$, $4078$ and $4109\text{A˚}$ group removed a different shifted group while preserving the one associated with $4358\text{A˚}$. These are actual selective-excitation controls, rather than inferred colours.^[ref]

The inference has limits. A complementary-filter test alone establishes newly admitted wavelengths, not their precise spacing or a unique microscopic mechanism. Fluorescence can also survive purification when intrinsic to the liquid, and fluorescence can be polarized. Useful distinctions therefore combine resolved spectral lines, excitation dependence, wave polarization and sample preparation. A proposed modern extension is to change a single incident frequency: a molecular Raman shift should follow the same internal energy gap, whereas ordinary relaxed molecular fluorescence usually retains approximately its emission-band positions. This is a diagnostic under stated conditions, not a universal theorem about every fluorescent material or resonant scattering process. Raman scattering need not involve a populated, relaxed electronic excited state as ordinary molecular fluorescence does; neither a redder photon nor the word Stokes identifies the mechanism by itself.

The 1930 Nobel Prize in Physics went to Chandrasekhara Venkata Raman alone for his work on scattering of light and the discovery of the effect. That award allocation should be distinguished from the joint experimental report with Kariamanikkam Srinivasa Krishnan.^[ref]

Precision X-ray emission spectroscopy turns closely spaced spectral lines into quantitative constraints on atomic energy levels. Bragg's law makes a crystal an angular ruler for wavelength: resolving nearby directions can reveal components hidden inside an apparently single line. Accurate line positions and the ability to separate two lines are related, but distinct, experimental achievements.

Karl Manne Georg Siegbahn received the 1924 Nobel Prize in Physics; his lecture was delivered on 11 December 1925.^[ref]

His son Kai Siegbahn received the 1981 Nobel Prize in Physics for electron spectroscopy.^[ref]

The Barkla characteristic X-ray experiment distinguished element-dependent K and L groups through absorption and excitation. Moseley's law related corresponding line frequencies across chemical elements to atomic number. Measuring the components within those groups asks a further question: which distinct atomic energy differences produce the neighbouring spectral lines?

Siegbahn's lecture organizes measured spectral lines into energy levels and resolved double levels.^[ref] The payoff is a map of atomic energy differences as well as an element's position in the periodic table.

A W boson decay can leave one visible charged lepton and a large missing transverse momentum; a Z boson decay can instead supply two visible leptons whose four-momenta determine an invariant mass. The two signatures answer the same existence question with different missing information. The electroweak unification history recognized by the 1979 Nobel Prize in Physics predates these 1983 observations: the W boson and Z boson were predictions to test, rather than particles first proposed in 1983.

The Super Proton-Antiproton Synchrotron stored counterrotating proton and antiproton beams; stochastic cooling made accumulation of the scarce antiprotons practical. Carlo Rubbia's 1984 lecture describes track reconstruction in a large drift chamber inside a magnetic field, surrounded by segmented particle calorimeters. Their nearly complete angular coverage allowed an imbalance test for unobserved neutrinos.^[ref]

Wireless telegraphy conveys discrete symbols without a connecting message wire. Here the mechanism is radio communication: keyed excitation produces radio waves, a receiving antenna drives a selective electrical circuit, and a detector produces a readable event. This makes a beautiful bridge between resonance and information: accumulating many appropriately timed small electrical disturbances can distinguish one transmission from another. Selectivity is finite, however; resonance alone cannot guarantee immunity to strong unwanted signals or noise.

The 1909 Nobel Prize in Physics recognized Guglielmo Marconi and Karl Ferdinand Braun for contributions to wireless telegraphy.^[ref] Their apparatus should be understood as a developing collection of systems. An early coherer receiver, a later tuned receiver and a modern envelope detector are different instruments.