Enthalpy

I've checked what corrections are usually applied to hydrogenoids (one electron around a nucleus), and they fit well the dataset from CE Moore, with no inertia from the electrostatic interaction. Here for the energy E of last ionization, where n=1 l=0. The relativistic correction to the mass depends on the local kinetic energy hence on the distance to the nucleus. That's the <Psi|p4|Psi> in Wiki's explanation of the perturbation method. Then, it increases the ionization energy by 2.5*E/mc2 rather than 1*. No mention of spin-orbit coupling has popped up for a spherical orbital, not even a quadratic effect. The Darwin term reduces the ionization energy by 2*E/mc2. The Lamb shift has no analytical expression nor excellent prediction beyond hydrogen. Subtracting a Z2 extrapolation from hydrogen would be exaggerated, and the fraction of Z2 drops nonlinearly with Z. The diagram shows (click for full scale): On X axis, the electron's ionization energy (taken as its kinetic energy) divided by its rest mass-energy; On Y axis, the relative deviation from a Z2 extrapolation from hydrogen. All hydrogenoids here are pinned, so the consequence of the nucleus' movement is removed by computation; The measures by C.E.Moore and their fit by a straight line that would be a Z2 relative, or Z4 absolute, deviation; The contribution by relativistic mass and Darwin, following both Z2 and already a nice fit of the measures; And the biggest possible contribution of Lamb shift to relativistic mass and Darwin. I've applied Z2 on the measured hydrogen Lamb shift (*23 for 1s instead of 2s). Picking some amount of Lamb shift would just fit the experiment. Some sources: https://en.wikipedia.org/wiki/Fine_structure https://en.wikipedia.org/wiki/Lamb_shift http://cua.mit.edu/8.421_S06/Chapter3.pdf http://crunch.ikp.physik.tu-darmstadt.de/nhc/pages/lectures/rhiseminar06-07/djapo.pdf Djapo.pdf gives on p34 a list of many contributions, where I don't see the inertia of the electrostatic interaction. So the mystery remains for me. We measure a mass for the electrostatic interaction of protons in heavy nuclei; the possible distributions of this mass should depend on the possible positions of the electron; but its inertia, which would be about as big as the relativistic mass correction, is unwanted to fit experimental data. The spreadsheet follows. Expand, open with GnuMeric or Excel. RelativisticHydrogen5.zip Marc Schaefer, aka Enthalpy

Hello you all! The present-day tárogató is a not-so-common woodwind with simple reed and conical bore like a saxophone, but with smaller tone holes, fingerings similar to an Oehler clarinet, body made of wood up to now, usually in C, played with clarinet mouthpiece and reed. Estimated 200 copies exist worldwide, mostly in Hungary and Romania. A record of a nicely played one, together with a hammered dulcimer: The tenor tárogató is truly rare - maybe one or two dozens worldwide. The ones I've seen use tenor saxophone reed, mouthpiece and neck, which make them sound more like a sax. Records: (begins at 12 min)and there too

A way to test the breakdown by visible and UV photons is to increase the feedback by adding mirrors. To concentrate light from the anode on the cathode, the left setup bounces it twice on parabolic mirrors, or maybe spherical ones. The right setup bounces light once (smaller losses) on elliptic mirrors, or maybe spherical ones. The right setup eases the insulation at the mirrors, and these can consist of several elements, for instance round ones. Aluminium offers unbeaten 0.8 reflection at 14eV and 0.6 at 15eV. If accepting 0.20, aluminium stops at 16eV, tungsten extends to 24eV and rhenium to 27eV = 46nm. Maybe the index step at Al2O3, TiO2, ZrO2 outperforms metals but it won't be easy. A combination of ceramics, optionally with metal? If the breakdown voltage varies with the area or number of mirrors, one could seek a relation with the solid angle exposed to the anode by the mirrors, and compare it with the cathode's one. Deep UV feedback is compatible with some observations. Smaller electrodes insulate better despite the field concentration, and a little bit of gas improves over vacuum. Marc Schaefer, aka Enthalpy

A lens to make the light's electric field more perpendicular to the photocathode was already proposed: https://www.researchgate.net/publication/238665413_FEASIBILITY_TEST_OF_LASER-INDUCED_SCHOTTKY-EFFECT-GATED_PHOTOCATHODE_RF_GUN ========== An experiment report about vacuum insulation, thanks: http://www.dtic.mil/dtic/tr/fulltext/u2/723107.pdf from 1971 but informative. I didn't read all reports, but many try to rescue somehow the disproven emission field model. It seems that Mankind lacks a good theory for vacuum insulation, despite many components rely on it. Measurements from 0µm through 1µm to 30µm distance, round AgNi electrodes: http://psec.uchicago.edu/Papers/Electrical_breakdown_of_small_gaps_in_vacuum.pdf observe 6kV breakdown at 30µm distance, so my unsubstantiated 8kV at 100µm look feasible. They may demand a cathode tip round instead of sharp, more so if the material has a low work function. ========== I suggested on 23 April 2017 that anode fluorescence and cathode photocurrent may cause vacuum breakdown. The linked report for Arpa suggested it already. A way to test this hypothesis for soft X-rays around 100kV is to deposit the same thin layer on varied anode materials like Al, Cu, Mo, Nd, W. The thin layer would give identical work function, optical properties, cleanliness, while the bulk materials vary the X-rays emission. Electrochemical means can deposit 5µm nickel. This lets electrons >40keV pass through, and attenuates X-rays >5keV by <2.7. Semiconductor processes achieve thinner layers of varied materials. For instance 500nm aluminium block visible light, let electrons >6keV pass through, and attenuate X-rays >500eV by <2.7. Thinner is easy. If different anode materials with identical coating give varied breakdown voltages, we can attribute it to X-rays feedback, and varied layer thicknesses indicate which X-ray energy range acts. If a difference is observed, it also suggests how to improve anodes. ========== If it hasn't been done yet, take banal cathode and anode materials but free of radioactivity, and observe the time to failure at ground level and in a tunnel or mine. Marc Schaefer, aka Enthalpy

Rather than "Auger", I meant "X-ray fluorescence". A thin layer of molybdenum might be more hermetic than cobalt.

A semiconducting anode would well detect energetic electrons (for instance photoelectrons) whose direct impact creates many carrier pairs. The arrangement is more compact and faster than the many dynodes of a photomultiplier. I had suggested it in 2008 for microscopic vacuum valves, and it is long known for other purposes. Gallium arsenide has a good hole and electron saturation speed, stopping power, resistance to beta rays, and it can integrate the fast preamplifier. Other semiconductors may be better, especially silicon for slower, thicker detectors. 1µm GaAs takes <10ps to collect the charges and stops >8keV photoelectrons that create 1900 pairs. This sketch has no scale. Horizontal and vertical dimensions aren't comparable. 160µm vacuum from the cathode to the anode take 6ps to cross, but I didn't check if the mean 50MV/m let the vacuum break down or provoke field emission. Over 1mm, the transit would increase to 37ps, but because the electrons' energy is uniform to better than +-1eV, the transit time would spread by +-300fs only. Operating near the field emission conditions would extend a photocathode's sensitivity to longer wavelengths. A broad guard ring at the cathode's potential, or even more negative, shall reduce the transverse speed of the emitted electrons. Modelling the field as hemispherical from R=15nm to the R<150nm guard ring, then flat to 160µm distance, the hemispherical part drops ~34V, so 34eV transverse energy let the electrons spread over R=10µm at the anode. A less pessimistic model would bring much. A D=30µm h=1µm GaAs (er=12.9) PIN diode has 80fF capacitance. A HEMT (transistor) on GaAs with 40fF input capacitance and 50ohm noise equivalent resistance creates 110µV = 13aC = 82q RMS noise over 15GHz bandwidth for 20ps bit duration, or +-11 sigma signal from one 8keV electron. Single photoelectron detection at >50Gb/s! The unpolarized diode adds no dark current, the modulation or pulse detection scheme shall make 1/F noise irrelevant, and 10nA gate leakage adds only 1q noise. The diode must be passivated and I don't trust an insulator. Maybe thin cobalt is hermetic enough. Additional metals are often needed for an ohmic contact. The passivation and the first electrode don't waste many pairs, as most appear where the incoming electron stops. If more than one photon created in the passivation or diode (including by radiative recombination) excites the cathode, the mode changes to sustained avalanche. Less convenient for datacomms, sometimes useful for instrumentation. By the way, we still don't have pleasant theories for vacuum breakdown to my knowledge, and this may be one. Integrating the preamplifier at the same chip and face as the diode reduces the parasitic capacitance hence the noise. A preamp at the rear face is nontrivial, stacked chips are possible. If the circuit must be protected from stray 8keV electrons (I didn't check), then >1.1µm aluminium stops the electrons and converts less than 500ppm of the energy flux in photons. 8keV photons would need the chip's thickness to attenuate by 105, but 1.5keV Auger photons are attenuated by e for every 370nm of cobalt thickness. If incoming light isn't perfectly concentrated, a carpet of resonating photocathodes, or a broad smooth photocathode, can target one semiconductor anode. A chip or module can integrate many semiconductor diodes and preamplifiers, for instance to make images or receive many parallel data paths. Marc Schaefer, aka Enthalpy

Hello everybody! The sarrusophone is a double-reed woodwind with conical metal body developed very shortly after the saxophone and sharing its fingerings. It lived shortly (enough for museums to have a few pieces) except for the C contrabass which was preferred in France to the contrabassoon for being louder. https://en.wikipedia.org/wiki/Sarrusophone A few (well over 100) copies still exist, and at least Benedikt Eppelsheim and Orsi produce them on request. Enough for musicians to blow in the horn with varied results. I've just heard one soprano nicely played, prompting me to share it: soprano alto tenor The record begins at 1min10. The sopranino, baritone, bass, Eb contrabass records also provided by Uriel Rodríguez S. over youtube aren't exceptional, but the soprano is impressive. Double reeds tend to have a harder sound to be improved by a narrow bore and small tone holes, and high-pitched instruments are more difficult to make and play, so I feared the worst from the soprano sarrusophone, but this one sounds just nice. Kudos to the musician!

Hello you all! Here, I suggest photocathodes that resonate at the light's frequency like a radiowave antenna to improve the sensitivity. As usual, I didn't check the state of the art, and since antennas for light exist already on solar cells, I could well be late. To increase the field, the cathode has a sharp tip like at some electron guns, and it shall resonate well, but metals are lossy at visible frequencies. Silver must be the best choice, followed by aluminium if the light isn't blue. From the CRC Handbook of Chemistry and Physics, section "optical properties of metals", for silver at 2eV = 620nm = 3*1015rad/s: The extinction coefficient k=4.18 so the current is shallow as compared to the wavelength; The reflectivity is still 0.944 so an incident wave of 1V/m that induces 5.2mA/m dissipates 150µW/m2; I deduce a surface resisitivity of 5.4 ohm/square. The tip needs a different material for emissivity but it conducts nearly no oscillating current. A cylindrical quarter-wave antenna of 30nm diameter with estimated 400nH/m has then j1,2Gohm/m and ohmic losses of 57Mohm/m hence an intrinsic Q~20, which is the desired improvement. If alone over the ground plane, it has also 36ohm radiation resistance which would much reduce the external Q, but we can spoil the radiation resistance and keep a decent inductance. For instance a reflector does that: wide enough, it adds little resistive losses, and if not too high, it lets the electrons escape. This can exaggerate up to a resonating cavity with a small hole letting the emitting tip through and some coupling for the light, like a small hole to adapt a fibre to the cavity. Dielectrics look less useful as they increase the ohmic losses. The antenna can have a wider base to reduce a bit the losses, for instance be conical (and longer to stay tuned). The light's electric field should be roughly parallel to the antenna. Often, flat photocathodes receive light from their normal direction, which I believe is suboptimum; a lens (punched as needed) with big numerical aperture should improve this, or a better orientation. One single antenna can receive light through a lens or from a fibre or guide; semiconductor processes can make the guide in addition to the antenna. Several antennas permit to cover a wider area; when used without a reflector, such an antenna catches electromagnetic power from a fuzzy area of 0.5*Lambda2/4pi, which tells what spacing is meaningful. Closer spacing broadens the frequency band but won't help the sensitivity. ========== A resonating photocathode, if better, has about the same uses as a traditional one. Some specific cases: An electron microscope needs an electron gun as brilliant as possible. Maybe a resonating photocathode improves that. I'd try warm sharp LaB6 at the tip. Multiphoton absorption is worth trying here with enough peak power, that is, even if the work function exceeds the photon energy. Future linear electron colliders have similar needs, but I suppose better answers exist already for them. Datacomms transport light on a tiny cross-section and need sensitive receivers. I already suggested to develop a photomultiplier tube with a small sensitive cathode spot http://www.scienceforums.net/topic/93628-observe-a-falling-charge-radiate/#entry910916 because photomultiplier tubes have already a small dark signal despite their big photocathode at room temperature. To my opinion, this is an easy research project that has good chances to work and is useful for physics instrumentation and for communications, including single-photon cryptography. The resonating photocathode would combine nicely with such a photomultiplier tube. Marc Schaefer, aka Enthalpy

Sorry I botched the estimate of the lithium battery. 100kWh per astronaut in a month, so 5 people over half a month nighttime need 900MJ, so the safe Li-poly battery weighs 2t, feasible. Optimize a bit, hope for lighter safe batteries - or send 2t there. With my sunheat engine, all becomes easier http://www.scienceforums.net/topic/76627-solar-thermal-rocket/page-3#entry900362

Hi JC and the others, thanks for the input! There is no hard limit to the thinness of a deposited film. When I worked in this field during the paleomonolithic era, aluminium films were commonly 1µm thick. On a Mylar space blanket it's rather 100nm. Presently with 14nm long transistors, metal layers are thinner than 10nm and still well reproducible. So I'm confident that thickness under 10nm can be achieved, which is adequate for most catalyst metals. Ruthenium and the most expensive metals are made thinner, so film evaporation may not be interesting for them. Fine, no solution is universal. An other criterium is "what catalyst area fits in a given volume". This differs from the thickness of the active metal because ultra-thin catalysts are supported, for instance on grains of an incompletely sintered ceramic, which are less small. The films I propose are few 10µm thick and can be packed to, say, 100µm stacking. This is roughly equivalent to a supporting powder with 100µm grain size, which is already interesting. While a porous sintered ceramic could be finer than 100µm grain size, the production method I propose adapts to about any catalyst metal, and the catalyst can be opened and cleaned.

Pure isotopes are available but expensive. Deuterium is less expensive. There are crystals made from pure isotopes. Seriously expensive, or rather, not marketed: produced without counting the costs when some research topic needs them. They help validate or invalidate some theories, like the superconductivity transition temperature of metals or the heat conductivity of silicon or diamond. I don't expect any signifiant effect on the electric conductivity of copper nor the magnetic permeability of iron (RMN deals with the nucleus' magnetic effect which is tiny, while efficient electrons act collectively in ferromagnetism). Certainly not enough to justify the cost. As ferromagnetism is a molecular property, there are cheaper are more efficient ways to influence it: by the alloying elements, the crystal size and orientation, and so on.

The momentum corresponding to the Moon's spin is much lower than the one corresponding to its orbit. Logically enough: different distances over the same time for the same mass.

The does of radiation is reduced by shields AND by short residence time. Apollo crews spent some time on low Earth orbit (just like the space station), "below" the belts because residual atmosphere cleans the particles away there, AND they passed quickly through the belts. The belts are lower near the poles and the atmosphere eliminates low particles there. This leaves some limited room "near" the Equator (51° inclination for the ISS nevertheless) where both the radiations and the density of the residual atmosphere are acceptable. Shielding means mass hence can't be perfect. Heavy elements are more efficient per kg but they create gamma rays when stopping charged particles, so at least the outer layers comprise only light elements like C, H, O, N and where needed Al. Magnetic shielding has been investigated and it failed to convince me. And some fraction of the radiation is too energetic to be stopped but still deposits some energy in the human body, so no miracle happens there. This is a concern for a trip to Mars. I didn't re-check, but from memory, the dose on the Moon was worse than when passing the van Allen belts. And it's said that the Apollo astronauts were lucky with the Sun's activity.

The square of the period varies like the cube of the orbital radius (or the big axis if elliptic).

Non-point mass distribution does result in non-Keplerian orbits. This is commonly used for observation satellites in sun-synchronous orbits, which are possible because the Earth isn't spherical but has a bulge at the Equator. https://en.wikipedia.org/wiki/Sun-synchronous_orbit

Energy, and even more decent temperature, is a BIG difficulty if wanting to spend the night on our Moon. Up to now, astronauts and probes have targeted the day side. I don't know of any one (I may have missed it) that passed a night there. Most plans want radioisotopic heat generators (which means 238Pu) to keep the probe on temperature. Yuk. If reducing the activity to nearly zero, a probe can hibernate during night time. My figures are there http://www.scienceforums.net/topic/85103-mission-to-bring-back-moon-samples/#entry919546 For a manned base, just digging in the soil keeps a reasonable temperature for the night. This is but necessary for the day too, and to protect against radiation, and against micrometeoroids, so the choice is already done. Some energy, that is electricity, is also necessary to a manned base, and lithium batteries are just good at that. Hydrogen and fuel cells can be considered; the benefit is discussable and the drawbacks clear. Flywheels and compressed gas store less energy per kg than batteries. Imagine that every astronaut needs 200kWh in 24h (3x my consumption but night is permanent there). Over 14 days, 5 people need 50GJ. Safe Li-polymer stores 500kJ/kg so this needs 100t batteries. This is a problem, so they will have to save energy a lot. Some heavy uses, like air and water recycling, can hopefully work during daytime only. Other solutions are difficult. Heat a big pile of regolith during daytime, extract energy from it during nighttime.

For 10m height, you don't need to burn propellants. Ejecting water from a bottle that contains as well air under pressure suffices. No risk of detonation then. https://en.wikipedia.org/wiki/Water_rocket

While the general idea isn't too wrong, the sentence cited in the first post uses inaccurate wording. Orbitals are stationary, so each and every word suggesting a movement is incorrect: "move", "most of the time" and so on. Was the question about "specific" electron? Then the answer is a clear "no". There is now way, in theory nor in experiment, to distinguish electrons. But this abuse is very common because proper wording is impractical. For instance, we may say "electron capture involves a 1s electron" but it isn't strictly correct. Problem: the true solution is a single wave function for all electrons, so there are no distinct orbitals in an atom with 3 electrons or more, and then we could forget any kind of reasoning. If the question was about electrons delocalized to both nuclei: yes. This is both modelled and observed. And the trick about paired electrons is only that opposite spins permit them to share the same orbital. When two atoms get close, the atomic orbitals interfere to create a favourable molecular orbital and an unfavourable one. The electrons ability to be both in the favourable one permits bonds. This depends on the number of electrons and the number of favourable orbitals. For instance N2 puts all electrons on bonding molecular orbitals so this bond is very strong and the molecule inert. O2 has two electrons more which must go to antibonding molecular orbitals, so the bond is weaker and the molecule active. F2 has again two electrons more, the bond is weak and the molecule reactive.

You mean, that one? https://en.wikipedia.org/wiki/Hydrogen-like_atom

A metal is full of electrons and holes. The effect of a pre-existing electrostatic charge is negligible. A much bigger amount of carriers flows between a metal and a semiconductor "when" the contact is established. Because of dirt, making mechanically a contact between a semiconductor part and a metal mart makes nothing predictable. Such "Schottky" contacts are produced by depositing the metal under vacuum over a clean semiconductor surface. https://en.wikipedia.org/wiki/Schottky_barrier As band diagrams show electron energies but electrons are negative; conventions are tricky. You could better tell whether the metal's Fermi level is in the semiconductor's valence band, conduction band or gap. Be aware that Schottky contacts use not to work as band diagram predict. They are plagued by surface states, which tend to make bad contacts even bands want ohmic contacts. So don't invest too much time here.

Agreed with the probabilistic approach, but just keep in mind that the wave function is much more than a way to compute probability densities. Especially, it is a complex number with a phase. The definition "not a product of separate wave functions" shows how general and common entanglement is. For instance, two electrons in a helium atom are entangled. If by some means you observe one electron in a small subvolume of the atom, then the other electron probably isn't there, because of their electric repulsion. The Schrö equation for both electrons includes this repulsion which would be seen in the solution if only we knew an algebraic solution. QM gets a little bit abstract at that point, at least to me, because the wave function for these two electrons in the fundamental state is still stationary. That is, no time involved here, except the term exp(iEt/hbar). The probability density is strictly static, so it's not when one electron is in a small subvolume, but if, that the other electron probably isn't. Even our language lacks simple expressions for that.

I don't see anything special with the band structure of InSb: http://www.ioffe.ru/SVA/NSM/Semicond/InSb/bandstr.html or did I miss something? Double post alas. See my answer in the other thread. A large band gap does not prevent recombination.

Ceramic capacitors do exploit permanent electric dipoles in the material, interacting enough to make a ferroelectric material (BaTiO3, SrTiO3, few more) if the temperature isn't too low. By adjusting the Curie temperature near the operation temperature (with Ba to Sr proportion); some achieve a permittivity like 200 000 but not infinity. The heterogeneous nature of ferroelectric materials must be the limit. The Curie transition is between "capacitive" and "permanent polarization" and it happens at different temperatures across the capacitor. These type II and type III capacitors are known by (some) users to show dielectric polarization, high losses and big temperature drift. Maybe a hypothetical homogeneous material would show one single transition temperature, but the permittivity would increase only at that temperature, and just below, it would bring pure losses.

The Helmholtz resonator is modelled as separated inductance (the neck) and capacitance (the belly), making it simple. A quarter-wave tube has no distinct neck and belly. It is modelled accurately with inductance and capacitance elements distributed all over the length, with a computation a bit more complicated. Though, there are similarities, because the the mouth of a tube, the pressure swing is small, so the capacitance has a smaller effect, and at the closed end, the speed is small, so the inductance has a smaller effect. So you get a not very wrong resonance frequency for a tube if you claim that the open half is a pure inductance nd the closed half a pure capacitance. Similarly, you could try to replace the belly of the Helmholtz resonator by an additional tube length of identical volume, but this is inaccurate when the added length adds much inductance, that is, when the diameters of the neck and belly differ much. Or you add a cylinder length that gives the same fundamental resonance frequency, but then the added volume won't match the belly's volume. And in any case, the overtones differ completely between a bottle and a tube.

A magnetic field can't be concentrated at distance nor have the shape of a beam in vacuum. An electromagnetic field can, within diffraction limits. It is done with light and with microwaves, including to transmit power, with bad efficiency. This needs antennas or lenses significantly bigger than the wavelength, hence big frequencies.