1/03/2021 Commemoration of the 125 years of the Discovery of Radioactivity 1

From Radioactivity to Modern Nuclear Physics:

125 years of discoveries

A. Lopez-Martens

Irène Joliot Curie Laboratory

Discovery of Radioactivity (1896-1898)

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Henri Becquerel Marie Curie Pierre Curie

« In recognition of the extraordinary

services he has rendered by his

discovery of spontaneous

radioactivity »

« In recognition of the extraordinary

services they have rendered by their

joint researches on the radiation

phenomena discovered by Professor

Henri Becquerel »

Nobel Prize in Physics 1903:

At the dawn of the 20th century

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“There is nothing new to be discovered in physics now.

All that remains is more and more precise measurement.”

attributed to William Thomson (Lord Kelvin), 1900British Association for the advancement of Science

Constituents of matter

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John Dalton

Dalton’s billiard ball, 1803

1803 :

-matter is made of atoms

-atoms of the same element are

identical

-atoms of an element can combine with those of

other elements to form compounds

-atoms of different elements have different masses

Classification of elements

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(1869)

Dmitri Ivanovich

Mendeleev

Regularities in the chemical

properties of the elements

Sc

Ga

Ge

The place of an element in the table is given by

the number Z (=atomic number, from AtomZahl)

A few clouds in the sky.....

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ultraviolet catastrophe

Max Planck

Matter can only absorb or emit

radiation energy in discrete packets

proportional to the frequency of the

radiation: energy quanta

Theory of special relativity: the laws

of physics are the same for all non-

accelerating observers, and the speed

of light in a vacuum is independent of

the motion of the observers

E=mc2

Albert Einstein

Failed Michelson-Morley experiment

The cathode tube leads the the revolution

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1895: Jean Perrin

demonstrates that cathode

rays are negatively charged

particles

Atoms are no longer indivisible !

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John Joseph Thomson

‘plum pudding’ model

1898: J.J. Thomson measures the charge/mass ratio of the charged

particles and concludes that what he calls ‘corpuscules’ (= electrons)

are the constituents of atoms

Magnet

Electric

capacitor

plates Scale

Power supply

From cathode rays to X rays

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Wilhelm Röntgen W. Röntgen receives the 1st Nobel Prize in Physics in 1901

1895 discovery of X rays

From X rays to Uranium rays

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1896 discovery of a spontaneous radiation emitted by Uranium

Henri Becquerel

Uranium rays ionize the air

and cause the discharge of

an electroscope

photographic plate

uranium saltsmetal screen

with cut-out

design

From Uranium rays to radioactivity

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1898: Marie Curie discovers that Thorium also emits Becquerel’s rays

Marie Sklodowska Curie

ionization chamber

electrometer

piezoelectric quartz

Notes aux Comptes Rendus de l’Académie des Sciences , April 1898

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1898: Pechblende is more « active » than Uranium

From Uranium rays to radioactivity

Laboratory at the Ecole de Physique et Chimie industrielle de Paris

Extraction of radium (Ba fraction)

Notes aux Comptes Rendus de l’Académie des Sciences , December 1898

Extraction of polonium (Bi fraction)

Notes aux Comptes Rendus de l’Académie des Sciences , July 1898

Radioactivity is manifold

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N

1898 E. Rutherfod alpha, beta radiation

1900 P. Villard gamma radiation

Ernest Rutherford

Aluminium ConcretePaper

radioactive

source

= hélium ion He2+

= high energy e-

= photons - like X raysPaul Villard

S

Atoms transform !

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1902 E. Rutherford & F. Soddy transmutation of atoms

Philosophical Transactions of the Royal Society of London, 1905

radioactivity

,

radioactivity

234Pa

Stable206Pb

234Th 230Th

238U

226Ra

222Rn

218Po

214Pb

214Po

210Pb

210Po

214Bi210Bi

234U

The rate of transmutation follows an exponential law

Frederick Soddy

Scattering of alpha particles

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Experiment performed by H. Geiger and E. Marsden

(1909, University of Manchester)

“It was almost as incredible as if you fired a 15-inch shell at a piece of

tissue paper and it came back and hit you! ”

0.1 Ci Ra emanation

The nucleus is born !

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16

Nuclear model

Philosophical Magazine 21, 669-688 (1911)

Num

ber

of dete

cte

d a

lpha p

art

icle

s

Scattering angle (degrees)

But, Rutherford’s atom is unstable !!

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Bohr solves the problem with Planck’s quanta

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• Electrons move around in orbits (shells) of fixed size and energy

• Known emission/absorption lines from atoms corresponds to electronic jumps from one orbit to another

Niels Bohr

Philosophical Magazine 26, 1-25 (1913)

Dalton’s atom undermined

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More than 40 radio-elements

discovered

in 15 years

Problem: There are only 7 empty

spaces in the periodic table between Bi and U!

‘The Chemistry of Radio-Elements’, F. Soddy (1911)

1913 Frederick Soddy

Concept of isotope: radioactive elements

with different masses but with the same

chemical properties

Inseparability of certain radio-elements

The periodic table finds its thread

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1914 Henry Moseley

Measurement of the high frequency spectra of many

elements

K emission

lines

atomic number Z = charge of the nucleus

regularities of the periodic table explained in terms of filling

of electronic shells

Alchemist’s dream come true

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1919 E. Rutherford 1st man-made transmutation

Rutherford calls H+ proton

α + Nitrogen → Hydrogen

The nucleus is thought to be composed of A protons and (A-Z) electrons

E. Rutherford suggests the existenceof an e--p pair, which would have allthe characteristics of a neutral particleBakerian Lecture, Proc. Roy. Soc. A, 97, 374 (1920)

H+ H+

H+ H+

e-

e-

e-

e-

This information goes unnoticed around the world, except at the Cavendish Laboratory in Cambridge, where Rutherford is appointed director...

The beginning of mass spectrometry

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Francis Aston

1919: F. Aston provides the experimental proof of the existence of isotopes

and measures isotopic abundances

He establishes that all masses (M(16O)=16) are whole

numbers, with the exception of Hydrogen (1.008) and

proposes that mass is lost to form nuclei

4 H

4He

reference lines due to H,C,O

and their compounds

A. Eddington suggests that the transformation

of H into He is the source of the sun’s energy

The theory of decay

22

1928: G. Gamow proposes a model for decay based on

quantum mechanics

Geiger-Nuttall law (1911)

Z. Physik 51, 204 (1928)

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Antimatter

1929 : Dirac equation

relativistic electron

Special Relativity Quantum Mechanics

The Dirac equation has 2 solutions !electron

????

electron

e–

e+

anti-electron

1930: P. Dirac invents the anti-electron1932 : C. Anderson discovers the anti-

electron and calls it positron

Discovery of the neutron

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1930-32 W. Bothe & H. Becker

discover a strange

reaction

I. Curie & F. Joliot

observe the ejection

of protons

James Chadwick

Proc. Roy. Soc., A, 136 (1932) 692

The mysterious radiation corresponds to a particle of mass ~1: the neutronionisation chamber

The nucleus is complete !

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1898 1911 1932

The presence of neutrons in the nucleus explains the phenomenon of isotopy

 

Z

AXN

1932: D. Ivanenko, W. Heisenberg and E. Majorana propose models of the

nucleus composed of Z protons and N neutrons. Heisenberg introduces isospin

Accelerators to probe the nucleus

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Cockroft-Walton voltage multiplier

J. Cockroft and E. Walton build a machine capable of

producing an accelerating voltage of 800 kVNature 129, February 1932, 242

Ernest Walton, Ernest Rutherforf, John Cockroft

1932: Cockroft and Walton “split the atom”

Nature 129, April 1932, 649

Artificial radioactivity

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1934 discovery of artificial radioactivity

13

27Al + 2

4He® X + n+ e+

13

27Al + 2

4He® 15

30P+ n

15

30P® e+ + 14

30Si

Irène Curie et Frédéric Joliotradio-phosphorus !

1936: John H. Lawrence is the first to use an artificial radio-element for therapeutic

purposes: 32P to treat leukaemia

The era of the neutron

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1934 E. Fermi proposes to bombard materials with neutrons

He demonstrates that nuclear transmutation occurs more readily with

slow neutrons

His group identifies 40 new radio-isotopes in 3 years

He proposes to irradiate heavy nuclei to synthesize transuranic elements and claims to

have produced the elements Z=93 et 94 (Ausonium et Hesperium)

n

The quest for transuranic elements...

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1935-1938: Otto Hahn, Lise Meitner and Fritz

Strassmann discover a great number of new

transuranium radio-isotopes (up to Z=96)

Lise Meitner and Otto Hahn (1918)

O. Hahn and F. Strassmann, Naturwiss 27 (1939) 11

“ We must name Barium, Lanthanum and Cerium, what we called

previously Radium, Actinium and Thorium. This is a difficult decision,

which contradicts all previous nuclear physics experiments.”

Irène Curie end Pavel

Savitch claim to have

produced a substance

similar to Lanthanum

(Actinium ?)

Fission

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L. Meitner and O. Frisch, Nautre 143 (1939) 239

1939:, Together with her nephew Otto Frisch, L. Meitner gives an explanation for the

observed phenomena: fission of uranium

This hypothesis is immediately confirmed by O. Frisch and by others (F. Joliot)O. Frisch, Nature 143 (1939) 276

N. Bohr et J.A. Wheeler develop a theory of fission based on the nuclear liquid

drop model N. Bohr et A. Wheeler, Phys. Rev. 56 (1939) 426

e-

e-

New discoveries

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1940: G. Flerov and K. Petrzak discover spontaneous

fission while studying Uranium nuclei

Gamma

Images by J. Giovinazzo

beta +

beta -

Alpha

Fission

Magic numbers

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Nuclei with a number of neutrons and/or protons equal to 20, 50, 82, 126 are relatively

more abundant than their neighbours

Nuclei associated with magic numbers are also exceptionally bound and give rise to

discontinuities with respect to the liquid drop energy

periodic structure of the nucleus ?

Maria G. Mayer

‘On closed shells in nuclei’, M G. Mayer Phys. Rev. 74 (1948) 235

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The question which solves the problem

S

L

‘On closed shells in nuclei. II’,

M. G. Mayer Phys. Rev. 75 (1949) 1969

Hans JensenM.G. Mayer et H.D. Jensen ‘Elementary Theory of Nuclear Shell Structure’, 1955

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Charge distribution within the nucleus

Some moments are 30 times larger than the shell-model prediction !

C.H. Townes et al., Phys. Rev. 76 (1949) 1415

And what if valence nucleons could polarize the nucleus... ?

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James Rainwater

Distortion of the liquid drop under the influence of the

trajectories of valence nucleons to gain in stability

J. Rainwater, Phys. Rev. 79 (1950) 432

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Single-particle and collective states of the nucleus

The unified model couples the oscillations and rotations of the liquid drop to the

movement of the individual nucleons

Aage Bohr et Ben Mottelson

Golden age of nuclear spectroscopy !

or e-

A. Bohr et B. Mottelson, Kgl. Danske Videnskab. Selskab, Mat-.-fys. Medd. 27 (1953) 16

Detection and acceleration developments

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Heavy ion beams

PMs, Scintillators & semi-conductors 160Gd(,4n)160Dy

12

10

14

12

16

14

18

16

Extreme shapes & multiple shapes

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P.J. Twin et al., Phys. Rev. Lett. 57 (1986) 811

T. Lauritsen et al., Phys. Rev. Lett. 88 (2002) 042501

Photons energy (MeV)

A.N. Andreyev et al., Nature 405, 430 (2000)

186Pb104

Extreme Elements

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Chemistry Department, University of Murcia

New Features

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J. Giovinazzo et al., Phys. Rev. Lett. 89, 102501 (2002)

M. Pfützner et al., Eur. Phys. J. A14, 279 (2002)

K. Miernik et al., Phys. Rev. Lett. 99, 192501 (2007)

Magic

Not magic

I. Tanihata et al., Phys. Rev. Lett. 55, 2676 (1985)

11Li 208Pb

A. Andreyev et al., Phys. Rev. Lett. 105 (2010) 252502

222Ra

P. Buttler et al.,, Phys. Rev. Lett. 124 (2020) 042503

125 years and 3312 nuclei later…

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M. Thoennessen et B. Sherrill, Nature 473 (2011) 25

Nuclear physics has many more surprises in store !

Start of RIBF in Japan

First stable and radioactive

beams at the next-generation

facilities SPIRAL2, RIA & FAIR,

new detectors & spectrometers

01/03/2020 Mon exposé - Lieu - Titre 42

Thank you for your attention