Discovery of helium

Andrii Sofiienko

PhD, Senior Physicist

Visuray AS

28th of May, Bergen

Table of Contents What is “Helium”?

Historical facts about Helium

Chemical and physical properties of 4He

Liquid Helium

Spectroscopy of 4He

Isotopes of Helium

Astronomy and 4He

Practical applications of 4He

Deficit of 4He in the future?

Escape of 4He into the space 28.05.2015 2

What is “Helium”?

Helium is a chemical element with symbol He

and atomic number 2. It is a colorless, inert,

monatomic gas that heads the noble gas group

in the periodic table [1].

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Fig. 1. The classical

representation of the

mulecula of 4He as a

nucleus with two

electrons on the orbit [2].

What is “Helium”?

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4

2He

Historical facts about Helium

The first evidence of 4He was observed on August 18, 1868 as a

bright yellow line with a wavelength of 587.49 nm in the spectrum of

the chromosphere of the Sun. The line was detected by French

astronomer Jules Janssen during a total solar eclipse in Guntur,

India [3], [4]. This line was initially assumed to be sodium.

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Fig. 2. Emission spectra of He and Na. Jules Janssen

(1824 - 1907)

4He

23Na

Historical facts about Helium

On Oct. 20, 1868, English astronomer Norman Lockyer observed a

yellow line in the solar spectrum, which he named the D3

Fraunhofer line because it was near the known D1 and D2 lines of

sodium [5]. He concluded that it was caused by an element in the

Sun unknown on Earth. Lockyer and chemist Edward Frankland

named the element with the Greek word ἥλιος (helios) [6], [7].

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Norman Lockyer (1836 - 1920)

Edward Frankland (1825 - 1899)

Historical facts about Helium

In 1882, Italian physicist Luigi Palmieri detected 4He on

Earth, for the first time, through its D3 spectral line, when he

analysed the lava of Mount Vesuvius [8].

On March 26, 1895, Scottish chemist Sir William Ramsay

isolated 4He on Earth by treating the mineral cleveite (a variety

of uraninite) with mineral acids. He noticed a bright yellow line

that matched the D3 line observed in the spectrum of the Sun

[9-11].

4He was independently isolated from cleveite in 1895 by

chemists Per Teodor Cleve and Abraham Langlet in

Uppsala, Sweden, who collected enough of the gas to

accurately determine its atomic weight [4], [12], [13]. 28.05.2015 7

Historical facts about Helium

In 1903, 4He gas (2%) was found in a natural gas field in

Dexter, Kansas. Helium of such concentration was found in a

number of other gas fields in the great plains in US.

In 1906, Hamilton P. Cady and David F. McFarland began to

analyze a large number of gas wells in Kansas, Oklahoma, and

Missouri. By the middle of 1906, they were able to report that

they had "a very unusual opportunity for obtaining helium

in practically unlimited quantities."

The USA is still the world’s largest supplier of helium, with many

reserves found in large natural gas fields (≈ 3·1010 m3).

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Historical facts about Helium On 10 July 1908, Heike Kamerlingh Onnes (Nobel Prize in Physics in 1978) was the first to liquefy 4He, using several precooling stages and the Hampson-Linde cycle (Joule-Thomson effect). He achieved the boiling point of 4He (−269 °C, 4.2 K). By reducing the pressure of the liquid 4He he achieved a temperature near 1.5 K [14].

28.05.2015 9

Heike Kamerlingh Onnes (1853 - 1926)

Fig. 3. Paul Ehrenfest, Hendrik Lorentz and Niels

Bohr visit Heike Kamerlingh Onnes (1919) in the

cryogenic lab [15].

Historical facts about Helium

Heike Kamerlingh Onnes tried to solidify 4He by further reducing the

temperature but failed because 4He does not have a triple point temperature at which the solid, liquid, and gas phases are at equilibrium.

Onnes' student Willem Hendrik Keesom was eventually able to solidify 1 cm3 of 4He in 1926 by applying additional external pressure of 2.5 MPa [1], [14].

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Willem Hendrik Keesom (1876 - 1956)

Historical facts about Helium

In 1938, Russian physicist Pyotr Leonidovich Kapitsa

discovered that 4He has almost no viscosity at T≈0K, a

phenomenon now called superfluidity [16]. This phenomenon is

related to Bose-Einstein condensation (Nobel Prize in Physics in

1978).

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Pyotr Leonidovich Kapitsa (1894 - 1984)

He-II will "creep" along surfaces to find its own

level, after a short while, the levels in the two

containers will equalize. The helium film (called a

Rollin film) also covers the interior of the larger

container; if it were not sealed, the He-II would

creep out and escape.

Historical facts about Helium In 1972, the same superfluidity phenomenon was observed in 3He, but at temperatures much closer to absolute zero, by American physicists Douglas D. Osheroff, David M. Lee, and Robert C. Richardson (they got Nobel Prize in Physics in 1996).

The phenomenon in 3He is thought to be related to pairing of 3He fermions to make bosons, in analogy to Cooper pairs of electrons producing superconductivity [17].

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Douglas D. Osheroff David M. Lee Robert C. Richardson

(1937 - 2013)

Chemical and physical properties of 4He

Property Value

Phase gas

Melting point 0.95 K (-272.2 °C) at 2.5 MPa

Boiling point 4.222 K (−268.928 °C)

Density

• Gas: 1.78·10-4 g/cc (20 °C);

• Liquid (m.p.): 0.145 g/cc;

• Liquid (b.p.): 0.125 g/cc;

Speed of sound • Gas: 970 m/s;

• Liquid: 180 m/s.

Ionization energy 24.47 eV

Mass excess 28 MeV

Magnetic moment [μN] 0 (-2.1276 in 3He)

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Table. 1. Several main chemical and physical properties of 4He [1, 2, 18, 19].

He is a colourless, odourless, insipid and non-toxic gas. It’s less soluble in

water than any other gas. It’s the less reactive element and doesn’t essentially

form chemical compounds. The termic conductivity and the caloric content are

exceptionally high [18].

Liquid Helium 4He exists in a liquid form only at the extremely low temperature of −268.928 °C (4.222 K).

Its boiling point and critical point depend on which isotope of helium is present: the common isotope 4He or the rare isotope 3He. These are the only two stable isotopes of helium.

Table 2. Some physical properties of two isotopes of He [20].

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Properties of liquid helium 4He 3He

Critical temperature 5.2 K 3.3 K

Boiling point at one atmosphere 4.2 K 3.2 K

Minimum melting pressure 25 atm 29 atm at 0.3 K

Density 0.145 0.082

Superfluid transition temperature at

saturated vapor pressure 2.17 K

1 mK in the absence

of a magnetic field

Liquid Helium

Usually different isotopes of the same substance differ only in their

mass. However, the He isotopes behave very differently at low

temperatures. [21].

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Fig. 4. The phase diagram of 4He. The liquid

has a phase transition to a superfluid phase,

also known as He-II, at the temperature of

2.17K (at vapor pressure). The solid phase has

either hexagonal close packed (hcp) or body

centered cubic (bcc) symmetry.

Fig. 5. The phase diagram of 3He. There are two

superfluid phases of 3He, A and B. The line within

the solid phase indicates a transition between spin-

ordered and spin disordered structures (at low and

high temperatures, respectively).

Liquid Helium

The reason for the different behaviour of 4He and 3He is

quantum mechanics [21].

4He is a boson. The appearance of the superfluid phase in 4He

is related to Bose condensation, where a macroscopic fraction

of the atoms is in the lowest-energy one-particle state.

3He is a fermion (like electron) and it is forbidden by the Pauli

exclusion principle that more than one fermion is in the same

one-particle state. The superfluidity arises from formation of

weakly bound pairs of fermions, so called Cooper pairs. The

pairs behave as bosons. In the superfluid state there is a

macroscopic occupation of a single Cooper pair state.

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Spectroscopy of 4He

Electron configuration: 1s2 4He has unique emission lines and Fraunhofer lines – discrete specra as usually in the gases [22].

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Spectroscopy of 4He

The absorption lines appear at precisely the same

wavelengths as the emission lines that would be produced

if the gas were heated to high temperatures [23].

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Spectroscopy of 4He and quantum mechanics

The Hamiltonian function of two electrons of 4He

(Werner Karl Heisenberg, 1926):

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120

2

20

22

2

2

10

22

1

2

44242ˆ

r

e

r

Ze

mr

Ze

mH

x y

z

e1 e2 r12

r1 r2

The last term represents electron-electron

repulsion at a distance r12.

)ˆ()ˆ(ˆiiiiii rErH

)ˆ()ˆ()ˆ,ˆ( 221121 rrrr

21 EEE

i(ˆ r i,i,i) Rni li(ˆ r i)li mi

(i,i)

Rn,l is the radial part;

Yl,m is the spherical harmonic.

Spectroscopy of 4He and quantum mechanics

The solution for the discrete energy states is:

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En Zeff

2e4

(40)22 2n2

Because the electrons are indistinguishable, the linear

combination of the wave functions also is a solution:

S 1

2( ( ˆ r 1) (ˆ r 2) ( ˆ r 1) ( ˆ r 2))

A 1

2( ( ˆ r 1) (ˆ r 2) ( ˆ r 1) (ˆ r 2))

Symmetric

Asymmetric

(ˆ r 1) (ˆ r 2)

Electrons in He can be in singlet state (asymmetric wave

function) or in triplet state (symmetric wave function).

Spectroscopy of 4He and quantum mechanics

Singlet states result when S=0.

Para-helium (~ 25%)

Triplet states result when S=1

Ortho-helium (~ 75%)

Triplet states are possible only

for the excided 4He due to the

Pauli exclusion principle.

Yellow line of 587.5 nm:

33D 23P

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Isotopes of Helium There are 9 isotopes of Helium with different numbers of

neutrons), stable and unstable [24]:

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2He 3He 4He 5He 6He 7He 8He 9He 10He

Mass excess: 28 MeV in 4He and 14.93 MeV in 3He.

Astronomy and 4He

Hydrogen is the most abundant element in the known Universe; helium is second.

The abundance of 4He (23% by mass) is well predicted by the standard cosmological model, since they were mostly produced shortly (~100 s) after the Big Bang, in a process known as Big Bang nucleosynthesis.

There are two reasons of the 4He production:

4He is stable and most neutrons combine with protons to form it because the excess energy is also high – 28 MeV;

Two 4He atoms cannot combine to form a stable atom: 8Be is unstable.

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Astronomy and 4He Solar Energy:

The Sun is by far the largest object in the solar system. It contains

more than 99.8% of the total mass. The Sun is, at present about

70% hydrogen and 28% helium by mass everything else ("metals")

amounts to less than 2% [34].

The Sun's power (about 386 billion billion MW) is produced by nuclear

fusion reactions. Each second about 700,000,000 tons of 1H are

converted to about 695,000,000 tons of helium (pp-cycle [35]):

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р + р → 2Н + е+ + νe (Eν < 0.42 MeV, τ ≈ 1010 y - weak interaction); 2Н + р → 3Не + γ + 5.49 MeV (τ ≈ 1.5 s); 3Не + 3Не → 4Не + 2р +12.86 MeV (65% - stellar core, τ ≈ 106 y); 3Не + 4Не → 7Ве + γ + 1.59 MeV (35% - stellar core, τ ≈5·105 y); 3Не + р → 4Не + νe + е+ + 18.77 MeV;

Practical applications of Helium

Today, He is used for many purposes that require some of its unique properties [1], [2]:

Cryogenics (32%)

Pressurizing and purging (18%)

Welding cover gas (13%)

Controlled atmospheres (18%)

Leak detection (4%)

Breathing mixtures (2%)

Other (13%, Neutron detection, zeppelins, …)

The balloons are perhaps the best known use of helium, they are a minor part of all helium use.

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Practical applications of 3He, 4He

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The largest single use of

liquid 4He is to cool the

superconducting magnets

in modern MRI scanners [1].

Medical imaging:

Polarized 3He (it can be stored

for a long time) has recently

started to be used in magnetic

resonance tomography for

imaging the lungs by means of

nuclear magnetic resonance

[27].

Practical applications of 4He A Helium Leak detector, also known as a Mass Spectrometer

Leak Detector (MSLD), is used to locate and measure the size of

leaks into or out of a system or containing device. The tracer gas,

helium, is introduced to a test part that is connected to the leak

detector. The 4He leaking through the test part enters through the

system and this partial pressure is measured and the results are

displayed on a meter [25].

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Practical applications of 4He

In rocket engines, 4He is often

used as a pressurizing agent,

pushing the liquid fuel and

oxidizer into the combustion

chamber [26].

4He is used for the purging of

the propellant feed systems

for liquid-hydrogen engines. 4He is used because its normal

boiling point is lower than that

of hydrogen. Other gases

would freeze, producing

particles that could clog

equipment [26].

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Practical applications of 3He 3He is a most important isotope in instrumentation for neutron

detection. It has a high absorption cross-section for thermal

neutrons. The neutrons are detected through the nuclear reaction

[27]

into charged particles tritium and protium that creates ionization in

the gas chamber.

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3 3 1 0.764n He H H MeV

Application:

Control of illegal

transport of radioactive

materials (Uranium

and Plutonium)

Practical applications of 4He A Zeppelin is a type of rigid airship named after Ferdinand

von Zeppelin who pioneered rigid airship development.

Zeppelin's ideas were first formulated in 1874 [28].

The Hindenburg was the largest airship ever built (97 people

on board, 1934). (It had been designed to use 4He, but the US refused to

allow its export. So, in what proved to be a fatal decision, the Hindenburg

was filled with flammable hydrogen – accident in May 1937, USA.)

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The first flight of LZ 1 over Lake Constance

(the Bodensee) in 1900 Ferdinand von Zeppelin (1838 - 1917)

Deficit of 4He in the future?

The diffusion speed of 4He through the solid materials is 3 times

more than of the air and by 65% more than of the hydrogen.

4He in the Earth's atmosphere escapes into space due to its

inertness and low mass. In a part of the upper atmosphere, 4He and

other lighter gases are the most abundant elements.

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In 1958 John Bardeen (the only person to

have won the Nobel Prize in Physics twice

[29]) and other influential scientists warned

the Congress that all our helium would be

gone by 1980. Congress reacted by spending

$1 billion on a separation plant in Amarillo,

Texas, and began stockpiling helium in empty

gas wells. John Bardeen

(1908 - 1991)

Deficit of 4He in the future?

After 1980, still worldwide consumption of 4He has

increased by 5 to 10% a year in the past decade

The USGS Mineral Resources Program (MRP) reported

in 2012 that current global consumption of 4He is around

180 million m3/year [30], [31].

There’s something like 50 billion cubic metres lying

around out there [30], [31]. That’s a near 280 years

supply at current usage rates up to 2292.

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Escape of 4He into space The atmosphere has a mass of about

5.15×1018 kg [30] three quarters of which is

within about 11 km from the surface.

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Composition of Earth's atmosphere by volume

is shown in right figure (1987 - 2009) [32].

∆Ratm ≈ 11 km

Vatm ≈ 5.6∙1018 m3

V4He ≈ 3∙1013 m3 (~10% of all 4He in Earth)

V3He ≈ 2∙108 m3 [27]

164 000 !He

He

production

Vyears

dV

dt

Escape of 4He into space The Earth’s atmosphere gradually leaks into space. The loss rate is currently only about 3 kg/s for hydrogen and 50 g/s for 4He [33].

Nature income of 4He from the Earth’s crust is about 67 g/s [36].

Considering the density of 4He at normal conditions the annual leakage is about 8.9 million m3/year – 20 times less that current production rate!

It needs about 3.33 million years to lose all 4He just from the atmosphere.

There are few reasons of the Helium escape:

Molecular evaporation in the exosphere (h>500 km, T<3000 K);

The upper atmosphere can absorb ultraviolet sunlight, warm up and expand, pushing air upward. As the air rises, it accelerates smoothly through the speed of sound and then attains the escape velocity. This form of thermal escape is called hydrodynamic escape or the planetary wind.

28.05.2015 34

Escape of 4He into space

Fig. 6. A schematic of the molecular evaporation of the gases from the

atmosphere [33]. 28.05.2015 35

Escape of 4He into space

Fig. 7. A schematic of the atmosphere wind effect that leads to the leakage of

the gases [33]. 28.05.2015 36

Escape of 4He into space

28.05.2015 37

EVIDENCE FOR

THERMAL ESCAPE

comes from considering

which planets and

satellites have

atmospheres and which

do not [33].

The deciding factor

appears to be the strength

of stellar heating (vertical

axis) relative to the

strength of a body’s

gravity (horizontal axis).

Airless worlds have strong

heating and weak gravity

(left of line). Bodies with

atmospheres have weak

heating and strong gravity

(right of line).

References 1. http://en.wikipedia.org/wiki/Helium

2. http://halo.wikia.com/wiki/Helium

3. Kochhar, R. K. (1991). "French astronomers in India during the 17th – 19th centuries". Journal of the British Astronomical Association 101 (2): 95–100.

4. Emsley, John (2001). Nature's Building Blocks. Oxford: Oxford University Press. pp. 175–179.

5. Clifford A. Hampel (1968). The Encyclopedia of the Chemical Elements. New York: Van Nostrand Reinhold. pp. 256–268.

6. Harper, Douglas. "helium". Online Etymology Dictionary.

7. Thomson, William (August 3, 1871). "Inaugural Address of Sir William Thomson". Nature 4 (92): 261–278.

8. Stewart, Alfred Walter (2008). Recent Advances in Physical and Inorganic Chemistry. BiblioBazaar, LLC. p. 201.

9. Ramsay, William (1895). "On a Gas Showing the Spectrum of Helium, the Reputed Cause of D3, One of the Lines in the Coronal Spectrum. Preliminary Note". Proceedings of the Royal Society of London 58 (347–352): 65–67.

10. Ramsay, William (1895). "Helium, a Gaseous Constituent of Certain Minerals. Part I". Proceedings of the Royal Society of London 58 (347–352): 80–89.

11. Ramsay, William (1895). "Helium, a Gaseous Constituent of Certain Minerals. Part II--". Proceedings of the Royal Society of London 59 (1): 325–330.

12. Langlet, N. A. (1895). "Das Atomgewicht des Heliums". Zeitschrift für anorganische Chemie (in German) 10 (1): 289–292.

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References 13. Weaver, E.R. (1919). "Bibliography of Helium Literature". Industrial & Engineering

Chemistry.

14. https://en.wikipedia.org/wiki/Heike_Kamerlingh_Onnes

15. https://en.wikipedia.org/wiki/Museum_Boerhaave

16. Kapitza, P. (1938). "Viscosity of Liquid Helium below the λ-Point". Nature 141 (3558):

74.

17. Osheroff, D. D.; Richardson, R. C.; Lee, D. M. (1972). "Evidence for a New Phase of

Solid He3". Phys. Rev. Lett. 28 (14): 885–888.

18. http://www.lenntech.com/periodic/elements/he.htm

19. http://www.dpva.info/Guide/GuidePhysics/Sound/SoundSpeedTable1/

20. https://en.wikipedia.org/wiki/Liquid_helium

21. http://ltl.tkk.fi/research/theory/helium.html

22. http://www.stmary.ws/HighSchool/Physics/home/animations3/modernPhysics/Emissio

nAbsorptionSpectra.htm

23. http://www.bluffton.edu/~edmistonm/astronomy/AT404/HTML/AT40401.htm

24. http://en.wikipedia.org/wiki/Isotopes_of_helium

25. http://www.heliumleakdetection.net/Helium-Leak-Testing/what-is-helium-leak-

detection.html 28.05.2015 39

References 26. http://quantum-technology.com/about/helium.html

27. http://en.wikipedia.org/wiki/Helium-3

28. http://en.wikipedia.org/wiki/Zeppelin

29. http://en.wikipedia.org/wiki/John_Bardeen

30. http://www.forbes.com/sites/timworstall/2012/08/27/what-great-helium-shortage/

31. http://minerals.usgs.gov/minerals/pubs/commodity/helium/mcs-2012-heliu.pdf

32. http://en.wikipedia.org/wiki/Atmosphere_of_Earth

33. D.C. Catling, K.J. Zahnle, The Planetary Air Leak, Planetary science, May 2009.

34. Bhargav Boinpally, Solar Energy, California Takshila University, 2010.

35. http://en.wikipedia.org/wiki/Stellar_nucleosynthesis

36. Andrew S. Balian, The Unintended Disservice of Young Earth Science, Infinity, 2011.

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Thank you for your

attention!

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