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Investigator sites log: Langmuir-Irving (Tonks and Langmuir, "Oscillations in Ionized Gases", Phys. Rev. 33, 195, 1929)

Run 1, 2026-10-04: the first run, so there were no prior sites to recheck. The search time limit was 10 minutes. The system clock recorded about 160 s between the first and last browser calls; that reading looks short, but the run stayed within the cap. All research was done in Chrome, in a new tab that was closed at the end. Google returned a CAPTCHA, so searching used Bing in Chrome plus direct site and API pages. No files were downloaded: the safety rules require the owner's explicit approval for any download, so the candidate files are listed under "Downloads awaiting approval". Per-visit notes are in research/2026-10-04-{site}.md.

Site URL First checked Last checked Queries tried Result Recheck? Notes
Google google.com 2026-10-04 2026-10-04 "Langmuir's paradox" electron scattering mercury arc plasma oscillations blocked (CAPTCHA) yes "unusual traffic" page; switched to Bing
Bing bing.com 2026-10-04 2026-10-04 6 queries (see Keywords) positive yes led to Baalrud 2009, Godyak 2015, PNAS 1928, Tonks 1967, LOC
APS journals journals.aps.org 2026-10-04 2026-10-04 DOIs PhysRev.33.990, PhysRev.55.1191, PhysRevLett.102.245005 positive yes abstracts only (paywall); Merrill and Webb 1939 abstract is key
UMich plasma theory group plasmatheory.engin.umich.edu 2026-10-04 2026-10-04 BaalrudPRL2009a.pdf positive yes open author copy of PRL 102, 245005; p.1 read from screenshot, pp.2-4 not read
IOPscience iopscience.iop.org 2026-10-04 2026-10-04 DOI 10.1088/0963-0252/24/5/052001 positive yes Godyak and Alexandrovich 2015 abstract
Crossref API api.crossref.org 2026-10-04 2026-10-04 6 bibliographic/author queries (see note) positive yes Tonks bibliography 1924-1936; 1930s-50s plasma-oscillation literature; the Penning query was negative
PNAS pnas.org 2026-10-04 2026-10-04 DOI 10.1073/pnas.14.8.627 positive yes Langmuir 1928 "Oscillations in Ionized Gases", PDF offered
AIP Publishing / AJP pubs.aip.org 2026-10-04 2026-10-04 (Bing result) Tonks "The Birth of Plasma" 1967 partial yes paywalled; page not opened
Library of Congress loc.gov 2026-10-04 2026-10-04 item mm77029413 positive yes Langmuir papers incl. lab notebooks 1894-1957; finding aid not yet opened
Nature nature.com 2026-10-04 2026-10-04 DOI 10.1038/176916a0 partial yes Gabor, Ash, Dracott 1955 "Langmuir's Paradox": metadata only
Internet Archive archive.org 2026-10-04 2026-10-04 title:(collected works irving langmuir) positive yes full 12-vol Collected Works scanned with OCR; Vol. 5 contents not verified
JSTOR jstor.org - - - not reached (time limit) yes PNAS 1928 copy; "Electron energy distributions in the low-pressure ..."
LOC finding aid ms012160 hdl.loc.gov/loc.mss/eadmss.ms012160 - - - not reached (time limit) yes search for Tonks, oscillation, plasma, scattering, 1925-29 notebooks
miSci / GE archives (Schenectady) misci.org - - - not reached (time limit) yes GE Research Lab records, Tonks papers, GE Review articles
AIP Niels Bohr Library (oral histories, ICOS) aip.org/history-programs - - - not reached (time limit) yes Tonks oral history?; Langmuir papers description
Google Patents / USPTO / Espacenet patents.google.com - - - not reached (time limit) yes Tonks and Langmuir GE patents on Hg-arc tubes and oscillators 1925-1935
plasmasensors.com plasmasensors.com/publications - - - not reached (time limit) yes author copy of Godyak 2015
Union College archives archives.union.edu - - - not reached (time limit) yes appeared in the LOC search; Schenectady holdings

Keywords tried

  • "Langmuir's paradox" electron scattering mercury arc plasma oscillations (Google, blocked)
  • "Langmuir's paradox" electron scattering plasma oscillations (Bing)
  • plasmatheory.engin.umich.edu Langmuir's Paradox Baalrud pdf (Bing)
  • Godyak "Langmuir paradox revisited" (Bing)
  • Langmuir 1928 "Oscillations in ionized gases" PNAS 14 627 (Bing)
  • Tonks "The Birth of Plasma" American Journal of Physics 1967 (Bing)
  • Irving Langmuir papers Library of Congress finding aid Tonks (Bing)
  • Crossref: Langmuir paradox revisited; author Tonks (to 1970); author Lewi Tonks (1929-1975); electron scattering plasma oscillations (to 1960); Gabor Ash Dracott Langmuir's paradox (to 1960); Penning high frequency oscillations discharge (to 1930)
  • archive.org: title:(collected works irving langmuir)

Keywords not yet tried (for the next run): "plasma-electron oscillations"; "electric sound waves" Tonks; "Lewi Tonks" obituary/oral history; Tonks Langmuir patent; "General Electric" "Research Laboratory" Langmuir mercury arc 1928; "Physics of electrical discharges" Tonks; Penning 1926 Physica "oscillaties"; Dittmer 1926 Phys. Rev. scattering; Langmuir 1925 "Scattering of electrons in ionized gases" Phys. Rev. 26, 585; "Langmuir oscillations" history; Bohm Gross 1949; zincite tellurium crystal detector; Schenectady Gazette 1928 Langmuir oscillations; "Tonks-Langmuir" ion oscillations confirmation; Revans 1933 oscillations.

Leads for review

1. The inventor's own work

  • Tonks and Langmuir, "Note on 'Oscillations in Ionized Gases'", Phys. Rev. 33, 990 (1 June 1929), DOI 10.1103/PhysRev.33.990 [web] https://journals.aps.org/pr/abstract/10.1103/PhysRev.33.990. The authors' own follow-up to the project document, four months later; content unknown (paywalled). It may correct the misprints the deep read found or add results. Bears on claims 1-3, possibly 4-5.
  • Langmuir, "Oscillations in Ionized Gases", PNAS 14(8), 627-637 (15 Aug 1928), DOI 10.1073/pnas.14.8.627 [web] https://www.pnas.org/doi/10.1073/pnas.14.8.627. Langmuir's earlier announcement of the same work; the PDF is free at PNAS. The JSTOR snippet says they had studied "these phenomena in detail during the last 4-5 years". [memory, high] It is the paper usually credited with naming "plasma". Bears on claims 1-5.
  • Tonks and Langmuir, "A General Theory of the Plasma of an Arc", Phys. Rev. 34, 876 (1929) [web] Crossref DOI 10.1103/physrev.34.876. The companion theory of the plasma and sheath, the setting for the scattering anomaly (claim 5).
  • Tonks, "The High Frequency Behavior of a Plasma", Phys. Rev. 37, 1458 (1931), and "Plasma-Electron Resonance, Plasma Resonance and Plasma Shape", Phys. Rev. 38, 1219 (1931) [web] Crossref. Tonks's own extension of the plasma-electron frequency to bounded plasmas. Claim 1 says the frequency is independent of the geometry of displacement; the 1931 "plasma shape" paper bears on that directly. Also bears on claim 2.
  • Tonks, "Impedance Characteristics of Loaded Lecher Systems", Physics 2 (1932), GE Schenectady [web] DOI 10.1063/1.1745024. Theory of the Lecher-wire method used to measure wavelengths in the 1929 experiments (claim 4).
  • Tonks, "Ionisation Density and Critical Frequency", Nature 132, 101 and 710 (1933) [web]. Applies the plasma frequency to ionospheric critical frequency (an extension of claim 1).
  • Tonks, "The Birth of 'Plasma'", Am. J. Phys. 35(9) (1967) [web] Bing/ADS. A first-hand history; abstract: "The author was there."
  • The Collected Works of Irving Langmuir (12 vols, 1960-62), full scans with OCR on the Internet Archive [web] https://archive.org/details/the-collected-works-of-irving-langmuir-vol.-5 (and the "electrical discharges" volume, collectedworksof0004drjd). [memory, medium] Vol. 5, "Plasma and Oscillations", reprints the PNAS 1928 paper, the 1929 paper and Note, and the 1925 scattering papers. Not verified this run. A possible route to the paywalled Note and a cleaner copy of the project document.
  • Langmuir papers, Library of Congress, mm77029413 [web] https://www.loc.gov/item/mm77029413/: laboratory notebooks 1894-1957, experimental sheets, correspondence. These are the primary lab records behind claims 4-5 (e.g. the 1.38 MHz resonance, the two-state arc, the 19-21 C critical oscillation).

2. Supporting information by others

  • Merrill and Webb, "Electron Scattering and Plasma Oscillations", Phys. Rev. 55, 1191 (1939) [web] https://journals.aps.org/pr/abstract/10.1103/PhysRev.55.1191. In a mercury arc with a movable probe, using a crystal detector and Lecher wires like the 1929 paper, they found narrow regions of stable periodic oscillations that coincided with the electron-scattering regions. Abstract: "The observed frequencies agreed well with the formula derived by Tonks and Langmuir"; they interpret the result "as showing that scattering is due to plasma oscillations which receive their energy from the fast electrons". 108 citing articles. Directly bears on claims 1 and 5 (and the "turbulent" noise of claim 4).
  • Baalrud, Callen and Hegna, PRL 102, 245005 (2009) [web] https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.102.245005; open copy https://plasmatheory.engin.umich.edu/wp-content/uploads/sites/519/2021/01/BaalrudPRL2009a.pdf. They propose that the anomalous scattering ("Langmuir's paradox") comes from ion-acoustic instabilities in the presheath, i.e. the "electric sound waves" branch of claim 3. They state the paradox "today remain[s] a serious discrepancy" and that no earlier work gave "a definitive answer". Bears on claims 3 and 5.
  • Linder, "Effect of Electron Pressure on Plasma Electron Oscillations", Phys. Rev. 49, 753 (1936) [web] Crossref. An early thermal correction to the zero-group-velocity result. Bears on claim 2 and extends the theory; it predates Bohm-Gross 1949 [memory, high].
  • Hernqvist (RCA), "Plasma Ion Oscillations in Electron Beams", J. Appl. Phys. (1955) [web] Crossref DOI 10.1063/1.1722036. Ion plasma oscillations observed in beams; bears on claim 3.
  • Gabor, Ash and Dracott, "Langmuir's Paradox", Nature 176, 916 (1955) [web] https://www.nature.com/articles/176916a0. Named the paradox; proposed sheath oscillations (per Baalrud 2009). Also Ash and Gabor, Proc. R. Soc. A (1955), "Experimental investigations on electron interaction", DOI 10.1098/rspa.1955.0063. Bears on claim 5 (an alternative oscillation mechanism).
  • Martin and Emeléus, "The Langmuir Paradox in Discharge Plasmas", Nature 177, 943 (1956) [web] Crossref. Bears on claim 5.
  • Godyak and Alexandrovich, "Langmuir paradox revisited", Plasma Sources Sci. Technol. 24, 052001 (2015) [web] https://iopscience.iop.org/article/10.1088/0963-0252/24/5/052001. High-resolution probe measurements in 1-3 mTorr argon found clearly non-Maxwellian distributions, attributed to non-local kinetics and standing striations. Evidence against the premise of the anomaly (claim 5), though in argon positive columns rather than Hg arcs. Stated here so the reviewers can weigh it.
  • 1940s-50s plasma-electron oscillation experiments: Armstrong, Nature 160, 713 (1947); Neill, Nature 163, 59 (1949); Wehner, J. Appl. Phys. (1951, Wright Field); Emeleus (1955-56); Dawson, Phys. Rev. 113, 383 (1959); Peterson and Puthoff, IRE Trans. (1959, ion plasma oscillations) [web] Crossref. A literature to mine for later measurements of claims 1-4.

4. Historical record

  • Library of Congress Langmuir papers (above). The finding aid hdl.loc.gov/loc.mss/eadmss.ms012160 is not yet searched.
  • Bing also surfaced AIP ICOS "Irving Langmuir papers, circa 1871-1957", Union College archives and a HathiTrust record (not opened).
  • The record does not go silent: the work continues openly through Tonks's 1931-34 papers, Merrill and Webb 1939, Gabor 1955 and Baalrud 2009. No absence-of-evidence anomaly has been identified so far. The open question is scientific (the mechanism of the scattering), not archival.

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