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第四組. 組員 : 杜佳霖 許銘亨 吳俊穎 杜文皓 黃煥純 鄭詠達. 化學報告. Discovery of Helium and the Rise and Fall of Coronium. Scientists know that our sun and other stars contain certain elements. 科學家們知道,我們的太陽和其他恆星含有某些元素。 How was this information obtained? 這些信息是如何獲得?

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Discovery of helium and the rise and fall of coronium

Discovery of Helium and the Rise and Fall of Coronium

Scientists know that our sun and other stars contain certain elements.

How was this information obtained?

In the early nineteenth century, the German physicist Josef Fraunhofer studied the emission spectrum of the

sun and noticed certain dark lines at specific wavelengths.

19

We interpret the appearance of these lines by supposing that originally a continuous band of color was

radiated and that, as the emitted light moves outward from the sun, some of the radiation is reabsorbed at

those wavelengths by the atoms in space.


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We interpret the appearance of these lines by supposing that originally a continuous band of color was

radiated and that, as the emitted light moves outward from the sun, some of the radiation is reabsorbed at

those wavelengths by the atoms in space.


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These dark lines are therefore absorption lines.

For atoms, the emission and absorption of light occur at the same wavelengths.

By matching the absorption lines in the emission spectra of a star with the emission spectra of known elements

in the laboratory, scientists have been able to deduce the types of elements present in the star.


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Another way to study the sun spectroscopically is during its eclipse.

In 1868 the French physicist Pierre Janssen observed a bright yellow line (see Figure 7.8) in the emission spectrum of the suns corona

during the totality of the eclipse.

18687.8)

(The corona is the pearly white crown of light visible around the sun during a total eclipse.)

This line did not match the emission lines of known elements, but did match one of the dark lines in the spectrum sketched by Fraunhofer.

Fraunhofer


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The name helium (form Helios, the sun god in Greek mythology) was given to the element responsible for the emission line.

Twenty-seven years later, helium was discovered on Earth by the British chemist William Ramsay in a mineral of uranium.

On Earth , the only source of helium is through radioactive decay processes particles emitted during nuclear decay are eventually

converted to helium atoms.


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The search for new elements from the sun did not end with helium.

Around the time of Janssens work, scientists also detected a bright green line in the spectrum from the corona.

They did not know the identity of the element giving rise to the line, so they called it coronium because it was only found in the corona.

Over the following years, additional mystery coronal emission lines were found.


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The coronium problem proved much harder to solve than the helium case because no matchings were found with the emission lines of

known elements.

It was not until the late 1930s that the Swedish physicist Bengt Edlen identified these lines as coming from partially ionized atoms of

iron, calcium, and nickel.

2030


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At very high temperatures (over a million degrees Celsius), many atoms become ionized by losing one or more electrons.

Therefore, the mystery emission lines come from the resulting ions of the metals and not from a new element.

So, after some 80 years the coronium problem was finally solved.

80

There is no such element as coronium after all!


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1937


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1800

1850 59

1860


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1663 21

1672 (Spectrum)(L.A.Senica 4 BC-65 AD)


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7500 (1 = )4000 (Visible Light VIS)

1800 (Sir WilliamHerschel 1738-1822) (Infrared IR)


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1781 2500 850 (Caroline.L.Herschel 1750-1848) (Sir John Herschel 1792-1871)


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  • IRVISUV

  • 1864 (J.C.Maxwell 1831-1879) 1888 (H.R.Hertz 1857-1894)


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Hz


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1802 (W.H.Wollaston 1766-1828)


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1814 (J.von Fraunhofer 1787-1826)

576

ABC...G


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D -D

1803 1804 (Wollastonite)31


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(A.S.Marggraf 1709-1782) 1762 () () () ()


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(W.H.F.Talbot 1800-1877)1825

1852 (A.J.Angstrom 1814-1874)


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(W.H.F.Talbot 1800-1877)1825

1852 (A.J.Angstrom 1814-1874)


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Optical emission spectrometer oes

(Optical Emission Spectrometer, OES)

(Optical Emission SpectrometerOES(spark)170 nm800 nm


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OES(Charge-Coupled Device CCD)Foundry-Master XPert


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10mm

3.5barArAr

Ar


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OES

GratingFocus Length(Charge-coupled DeviceCCD)

(1)

(2)

(3)

(4)

(5)


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OES20()


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FE_000

Orientation

FE_100

Low alloy steel

FE_150

Free cutting steel

FE_200

Cast

FE_250

High Cast alloy

FE_300

Cr-/Ni-Steel

FE_400

Tool Steel

FE_500

Mn-steel

Al _000

Al-Global

Al _100

Low alloy aluminum

Al _200

Al-Cu alloys

Al _300

Al-Mg alloys

Al _400

Al-Si alloys

Al _450

Al-Si-Cu alloys

Al _500

Al-Zn alloys

Cu _000

Cu-Global

Cu _200

Cu-Zn alloys

Cu _300

Cu-Sn-Pb alloys

Mg _000

Mg-Global

Ti _000

Ti -Global

OES


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(R.W.Bunsen 1811-1899) (G.R.Kirchhoff 1824-1887)D D D 1859


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D D

185963 11


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NO


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Pierre Jules Csar Janssen182422219071223

1868818587.49


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Joseph von Fraunhofer178736182667

11180181818

1824

39

1814 574


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  • KCBSir William Ramsay185210219167231904

  • 1852

  • Investigations in the Toluic and Nitrotoluic Acids18791881Margaret Buchanan

  • 188718851890


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18944198189519031910-

1904

19167231976


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