chapter 4 structure of the atom

Chapter 4Structure of the Atom

4.1 Early Theories of Matter4.2 Subatomic Particles & Nuclear Atom4.2.5 Ultimate Structure of Matter – The Standard Model (Not in Book)4.3 How Atoms Differ4.4 Unstable Nuclei & Radioactive Decay

Beyond proton/neutron/electron Picture

Textbook, page 97

“the three subatomic particles you have just learned about have since been found to have their own structures. That is, they contain sub-subatomic particles. … will not be covered … because it is not understood if or how they affect chemical behavior.”

Beyond proton/neutron/electron Picture

Yes boys and girls, this is where we leap off the deep end!

Beyond proton/neutron/electron Picture (not in book)

To understand nucleus and how some nuclear radiation processes occur, need to examine both structure of nucleons (proton, neutron) and forces acting at nuclear distances

The standard model of physics attempts to describe all known forces and elementary particles

What Is Matter ?Matter is all the “stuff” around you!

The big picture (from standard model):

Hadrons

Matter

Leptons

Baryons Mesons Charged Neutrinos

Forces

Weak EM

StrongGravity

QuarksAnti-Quarks

Launch Realplayer video from Fermilab SiteProduced by Fermilab

atoms proton/neutron/electron quarks antimatter leptons wave/particle duality electron diffraction

Particles

http://vmsstreamer1.fnal.gov/VMS/VideoNews/VN77-Particles.ram

Antimatter – Paul DiracIn 1928, wrote down equation which combined quantum theory (developed in 1920s by Schrodinger and Heisenberg) and special relativity (1900s, Einstein), to describe behavior of electron

Equation could have two solutions, one for electron with positive energy, and one for electron with negative energy

But in classical physics (and common sense!), energy of particle must always be a positive number!

http://livefromcern.web.cern.ch/livefromcern/antimatter/history/AM-history01.html

Antimatter – Paul DiracDirac interpreted this to mean that for every particle that exists there is a corresponding antiparticle, exactly matching the particle but with opposite charge

For electron, for instance, there should be an "antielectron" identical in every way but with a positive electric charge

In Nobel Lecture, Dirac speculated on existence of completely new Universe made out of antimatter!

http://livefromcern.web.cern.ch/livefromcern/antimatter/history/AM-history01.html

Paul Dirac

Antimatter – Carl Anderson1932, young professor at Caltech, studied showers of cosmic particles in cloud chamber; saw track left by "something positively charged, and with the same mass as an electron"

After nearly 1 year of effort and observation, decided tracks were actually antielectrons, each produced alongside an electron from impact of cosmic rays in cloud chamber

Called antielectron "positron", for its positive charge. discovery gave Anderson the Nobel Prize in 1936 and proved existence of antiparticles as predicted by Dirac http://livefromcern.web.cern.ch/livefromcern/antimatter/history/AM-history01-a.html

Anderson's cloud chamber picture of cosmic radiation from 1932 showing for first time the existence of anti-electron

Particle enters from bottom, strikes lead plate in middle and loses energy as can be seen from greater curvature of upper part of track

http://www.aps.org/publications/apsnews/200408/history.cfm http://livefromcern.web.cern.ch/livefromcern/antimatter/history/AM-history01-a.html

Antimatter – Carl Anderson

AntimatterAnderson close to his cloud chamber

http://livefromcern.web.cern.ch/livefromcern/antimatter/history/AM-history01-a.html

Quantum Mechanics & AntimatterNobel Prize, 1933 Erwin Shrodinger (Berlin U, Germany), Paul Adrien Maurice Dirac (U Cambridge, UK)

“for the discovery of new productive forms of atomic theory”

AntimatterNobel Prize, 1936 Hess (Innsbruck U, Austria), Anderson (Caltech)

Hess: for his discovery of cosmic radiation

Anderson: for his discovery of the positron [first confirmation of the existence of antimatter]

Matter & Forces from Standard Model

Hadrons

Matter

Leptons


Forces

Weak EM

StrongGravity

QuarksAnti-Quarks

Particles in Standard ModelSix leptons are all elementary particles – includes the electron

All other particles (hadrons) are composed of combinations of quarks (6 kinds) – isolated quarks are not permitted

Class of hadrons called baryons composed of 3 quarks – includes proton & neutron

Class of hadrons called mesons composed of 2 quarks (quark + anti-quark)

“Ordinary” matter

Standard Model

The Standard Model

Launch “The Standard Model” (Running time 6:36) Launch QT Video (stream) from Web

http://www.pbs.org/wgbh/nova/elegant/media2/3013_qd_04.html

Standard ModelFour Fundamental Forces

In order of decreasing strength:Strong – binds nucleons Electromagnetic – “opposites attract”Weak – involved in radioactive decay (beta decay)Gravity

Forces arise through exchange of a mediating field particle (a boson)

Four Fundamental Forces

?

Standard Model Basic Particles and Force Carriers

All 6 quarks and 6 leptons have corresponding antiparticles with opposite charge

Some particles are their own antiparticles

“Colors” Of Quarks

Quarks are said to have colors (thought of as charge but 3 types)

Colors – blue, red and green

3 colors of quark are attracted together

Antiquarks have cyan, magenta, yellow

Works by exchange of gluons: called strong force

Structure within Proton (with gluons – animation)

Structure within Proton

p-

po

p+

L+

p

S0

D++

Do

D+

D-

W-

K+

K0

K-

W h a t a j u n g l e !

Dimensions of Subatomic Particles

If protons and neutrons were 10 cm across, then quarks and electrons would be < 0.1 mm in size and entire atom would be ~ 10

km across

Structure Within the Atom

Space is mostly “empty space”

Atoms > 99.999% empty space

Electron

Nucleus

Protons & Neutrons are > 99.999% empty space

g

u d

u

Quarks make up negligiblefraction of

protons volume !!

Proton

The Universe

The universe and all the matter in it is almost all

empty space !

(YIKES)

Why does matter appear to be so rigid ?

Forces, forces, forces !!!!

Primarily strong and electromagnetic forces which give matter its solid structure

Strong force defines nuclear size

Electromagnetic force defines atomic size

Standard Model Development

Developed by careful analysis of high energy physics experiments (particle accelerators and colliders)

Lots of heavy thinking!

Standard Model Related Nobel Prizes

1948 Blackett (Victoria U, Manchester, UK)

for his development of the Wilson cloud chamber method, and his discoveries therewith in the fields of nuclear physics and cosmic radiation


1949 Yukawa (Kyoto Imperial U, Japan)

for his prediction of the existence of mesons on the basis of theoretical work on nuclear forces


1950 Powell (Bristol U, UK)

for his development of the photographic method of studying nuclear processes and his discoveries regarding mesons made with this method


1957 Yang (Institute for Advanced Study, Princeton), Lee (Columbia U)

for their penetrating investigation of the so-called parity laws which has led to important discoveries regarding the elementary particles


1959 Segre, Chamberlain (both U Cal. Berkeley)

for their discovery of the antiproton

Standard Model Related Nobel Prizes1963 Wigner (Princeton), Goeppert-Mayer (U Cal. La Jolla), Jensen (U. Heidelberg, Ger.)

Wigner: for his contributions to theory of atomic nucleus and elementary particles, particularly through discovery and application of fundamental symmetry principles

Goeppert-Mayer, Jensen: for their discoveries concerning nuclear shell structure


1965 Tomonaga (Tokyo U. of Education), Schwinger (Harvard), Feynmann (Caltech)

for their fundamental work in quantum electrodynamics, with deep-ploughing consequences for the physics of elementary particles

Standard Model Related Nobel Prizes1969 Gell-Mann (Caltech)

for his contributions and discoveries concerning the classification of elementary particles and their interactions

Proposed new quantum property of particles he called "strangeness number." Found even more general characteristics that allowed him to sort particles into eight "families" - called this grouping the eightfold way, referring to Buddhist philosophy's eight attributes of right living. Found that eightfold way could best be explained by a particle, undiscovered as yet, with 3 parts (hadrons), each holding a fraction of a charge. [Named and predicted existence of quarks.]

Standard Model Related

Lawrence P. Horwitz

Algebraic approach to quark modelIn 1964, there were many expositions on the “quark model" of hadronic physics at CERN, and Horwitz (then at U of Geneva) brought the question to Yuval Ne'eman whether these results could be explained in term of group theory rather than the very questionable dynamics of such strongly interacting systems. They succeeded (with N. Cabibbo) in developing a group theoretical model which was very successful, and later justified its structure in terms of the asymptotic forms proposed by Gell-Mann and his student Melosh.

http://www.telesio-galilei.com/L%20P%20Horwitz%20Summary%20of%20Scientific%20Contributions.pdf

Ms. Simon’s Father


1976 Richter (Stanford Linear Accelerator Lab), Ting (MIT)

for their pioneering work in the discovery of a heavy elementary particle of a new kind


1979 Glashow (Harvard), Salam (Imperial College London) & Weinberg (Harvard)

Theory of the unified weak and electromagnetic interaction

(Weinberg coined term “standard model”)


1984 Rubbia & van der Meer (both CERN, Geneva)

Discovery of field particles W and Z, communicators of weak interaction


1988 Lederman (Fermilab, Batavia, IL), Schwartz (Digital Pathways Inc, Mountain View, CA), Steinberger (CERN, Geneva)

for neutrino beam method and demonstration of doublet structure of leptons through discovery of muon neutrino

Standard Model Related Nobel Prizes1990 Friedman (MIT), Kendall (MIT), Taylor (Stanford U)

for their pioneering investigations concerning deep inelastic scattering of electrons on protons and bound neutrons, which have been of essential importance for development of the quark model in particle physics


1995 Perl (Stanford), Reines (U Cal. Irvine)

for pioneering experimental contributions to lepton physics: Perl “for the discovery of the tau lepton”; Reines “for the detection of the neutrino”


1999 ‘t Hoof (Utrecht U., Netherlands), Veltman (Bilthoven, Netherlands)

for elucidating the quantum structure of electroweak interactions in physics


2004 Gross (U Cal. Santa Barbara), Politzer (Caltech), & Wilczek (MIT)

Discovery of asymptotic freedom in the theory of the strong interaction

Standard Model Related Nobel Prizes2008 Nambu* (U Chicago), Kobayashi** (High Energy Accelerator Research Org., Japan), Maskawa** (Yukawa Institute for Theoret. Physics, Kyoto U., Japan)

*for the discovery of the mechanism of spontaneous broken symmetry in subatomic physics

**for the discovery of the origin of the broken symmetry which predicts the existence of at least three families of quarks in nature

Unsolved Mysteries

The following topics are areas of active research in the physics community

Elementary Particles if Strings Exist

(Lepton)

(Baryons)

Particle Accelerators

Charged particles, like protons, whipped around, bang into another high speed particle and break apart

Pieces don’t last long, only 10-7 s to 10-24 s

Data used to discover existence of quarks and other “exotic” particles

Aerial View of Fermilab

“Doubly Strange" ParticleSept. 3, 2008

Physicists of the DZero experiment at the U.S. Department of Energy's Fermi National Accelerator Laboratory have discovered a new particle made of three quarks [baryon], the Omega-sub-b (Ωb).

Particle contains two strange quarks and a bottom quark (s-s-b). It is an exotic relative of the much more common proton and weighs about six times the proton mass.

“Doubly Strange" ParticleCombing through almost 100 trillion collision events produced by the Tevatron particle collider, the DZero collaboration found 18 incidents in which the particles emerging from a proton-antiproton collision revealed distinctive signature of the Omega-sub-b.

Once produced, the Omega-sub-b travels ~ a millimeter before it disintegrates into lighter particles. Its decay, mediated by the weak force, occurs in about a trillionth of a second.

“Doubly Strange" Particle"The observation of the doubly strange b baryon is yet another triumph of the quark model," said DZero cospokesperson Dmitri Denisov, of Fermilab. "Our measurement of its mass, production and decay properties will help to better understand the strong force that binds quarks together.“

“Doubly Strange" ParticleAccording to the quark model, invented in 1961 by theorists Murray Gell-Mann and Yuval Ne'eman as well as George Zweig, the four quarks up, down, strange and bottom can be arranged to form 20 different spin-1/2 baryons. Scientists now have observed 13 of these combinations.

“Doubly Strange" Particle

DZero is an international experiment of about 600 physicists from 90 institutions in 18 countries. It is supported by the U.S. Department of Energy, the National Science Foundation and a number of international funding agencies.

Some DZero Scientists in Front of the

DZero Detector

Links for Those Who Want More

Fermilab Physics For Everyone Lectures

“Particle Physics: The World of Matter, Space, and Time” November 14, 2000 00:47:04

http://vmsstreamer1.fnal.gov/Lectures/Physics4Every/Quigg/index.htm

Link to main Video Search

Fermilab Physics Videos Main Search PageChoose “General Interest” or “Student” levels or specific series (e.g. “Physics for Everyone”) or other topics of interest

http://vmsstreamer1.fnal.gov/Lectures/Physics4Every/Quigg/index.htm

http://vms-db-srv.fnal.gov/fmi/xsl/VMS_Site_2/000Search/video/f_streaming.xsl

Launch Video from Nova Science Nowhttp://media.pbs.org/asxgen/general/windows/wgbh/nova/nsn-3410-02-350.wmv.asx

12 min 20 sec

Particle Physics at CERN

Particle Physics at CERN

http://www.pbs.org/wgbh/nova/sciencenow/3410/02.html

http://media.pbs.org/asxgen/general/windows/wgbh/nova/nsn-3410-02-350.wmv.asx



Launch Video from MiscLHC (CERN) Rap (by Alpinekat)

See YouTube

CERN – Large Hadron Collider LHC

LHC Technology Review (MIT) May/June 2008 By Jerome Friedman

The recently completed Large Hadron Collider, the world's most powerful particle accelerator and most ambitious scientific instrument, is being readied to address some of the deepest questions in physics. Hundreds of feet below the surface of the earth, straddling the Swiss-French border near Geneva, it will smash counter-rotating, seven trillion-electron-volt beams of protons against one another in a 27-kilometer ring of superconducting magnets.

LHC With this immense energy, the LHC will be capable of producing new types of particles that are thousands of times heavier than the proton. And it will enable physicists to study phenomena at one-ten-billionth the scale of the atom.

The science will be carried out with five multisystem particle detectors, the most massive of which are Atlas and CMS. Atlas is comparable in size to a seven-story building, 135 feet long and 75 feet wide; CMS, a somewhat smaller but heavier detector, weighs more than one and a half times as much as the Eiffel Tower.

Compact Muon Solenoid CMS (high energy particle physics detector) at CERN lab (Geneva)

Will be largest solenoid ever built

Maximum magnetic field 4 Tesla (~100,000 x strength of Earth’s field)

Amount of iron used roughly equivalent to that used to build Eiffel Tower

Very Large Solenoid (CMS)

Higgs Boson - Fermilab vs CERN

4/2/08

Fermilab is perhaps best known for its particle accelerator, the Tevatron. Currently the largest and most powerful accelerator in the world, the Tevatron’s name originates from how it can accelerate protons and antiprotons to energy levels as high as one trillion electron volts, or one TeV.

Its position will soon be usurped, however, by the Large Hadron Collider (LHC) at CERN in Geneva, Switzerland. A multi-million dollar effort by the European Union, the LHC is expected to officially begin operations in May 2008.

http://www.thetriplehelix.org/uncategorized/928

Fermilab makes its own antiprotons to be used in Tevatron, and prevents them from interacting with matter by holding them in place with magnetic fields. LHC, in contrast, will use proton-proton collisions, a decision influenced by difficulty of obtaining antimatter—one million protons are required to generate an average of 10 antiprotons.

Both Tevatron and LHC have one main objective: to obtain grand prize of particle physics, the Higgs boson. In the Standard Model of particle physics that describes three of the four fundamental forces in the universe, only gravity, or the origin of mass, remains unexplained.


The Higgs boson, thought to give mass to other particles, is the missing piece of the puzzle. It has escaped detection so far, but scientists hope that the energy levels the LHC can provide—up to 14 TeV—will be high enough to finally provide a glimpse of the elusive particle. The pursuit of the Higgs at Fermilab is also a race against the clock, since the Tevatron is scheduled to shut down in 2009 .


Higgs Boson vs Gravitonhttp://www.physicsforums.com/showthread.php?t=78993

I hope I'm posting in the right place. I was just wondering, what is the difference between the graviton and the higgs boson. I'm not quite sure, I think I sort of understand it... but not really.-----------------------------------------------------------------------------------The higgs boson is the field that interacts with particles to give them mass. Think about it as the answer to the question: Where does mass come from? The answer is: from the interaction between the particle and the higgs field.

The graviton, is the theoretically predicted quanta of the gravitational field. If a quantum field theory of gravity exists, the graviton would be the particle which mediates the gravitational force much like the photon for QED.


The Higgs gives particle the property of mass. Once the particle has mass, it eminates a gravitational field. The gravitons are the mediator of this gravitational interaction.---------------------------------------------------------------------------------------Look the Higgs is a postulated particle. It was born as a mathematical trick in order to solve some problems concerning symmetry in quantum field theory. The Higgs has mass because we defined it like that. The Higgs particle gives mass to elementary particles via it's interaction with these particles. This interaction can be expressed in terms of a coupling between the higgs field and the elementary particle field. The coefficient of the product of these fields is the mass of the elementary particle. This is just how the QFT formalism works.


(continued)This is very interesting stuff but not that easy.Also i read analogy stuff like 'the gravitons are the photons'. Do not pay any attention to this because it is fundamentally wrong. Gravitons are very different in nature, they indeed mediate the gravitational force but they are different in nature because they ARE particles of space time itself

Higgs Boson: How to Detecthttp://www.physicsforums.com/showthread.php?t=203001

The Higgs is one of those particles that can't be detected directly because it will not tend to survive long enough to hit a detector. This is okay because we can calculate, when the particle decays, what it decays into. So if you look in the right places, you will find descriptions of the various paths for "production" of various kinds of particles. The idea is that at a certain energy scale there are a certain number of ways a Higgs could come into being, and a certain number of things that are likely to happen when a Higgs is produced. Since we know a lot about the Higgs, we can calculate ahead of time what those things will be.

(continued)


I can't find right now a description of the paths we'll likely see at the LHC, but here's a description of how they're looking for the Higgs at the Tevatron, from the blog of a scientist there, which should give you a rough idea.

(continued)


The short version of the Tevatron description as I'm reading it is: the Tevatron particles crash, and the energy of that crash could produce a number of things. Among the things it could produce is a Higgs, or it could also produce a W Boson and a Higgs, or maybe a Z Boson and also a Higgs. Meanwhile, once the Higgs comes into being, it will last for a certain amount of time, after which it could decay into a b-quark and a b-anti-quark, or it could decay into a pair of W bosons. Of course, the W bosons and such aren't directly observable either! They decay into other things... some of which decay into other things... eventually, all this decaying is done, and the particles that are left over are long-lived ("long-lived" meaning "long enough to travel a a few feet away to the detector") things like neutrinos. THESE are the things that the detector detects!(continued)


So basically, you're running this detector. With each collision you get a weird smattering of particles hitting the detector, and for each particle your detector registers things like its energy, its angle, whatever. And you sit down with a mathematical model that has a long, long list of all the different things that could possibly be produced in a collision; and for each of those things that could be produced, it has a list of "decay channels" (or in other words, a list of final states, saying for example that after all the decaying is done, you'll get 4 particles of this type arriving at these sorts of angles at this time, and then 3 particles of this other type arriving... etc). Each of these productions will have a different probability, and each decay channel/final state will have a different probability of resulting from its initial particle production. (continued)


So you try to match up the things your detector found, with these final states. Because so much of your model is based on probabilities, you have to do this statistically-- you have to measure a huge number of events, and then you measure whether the number of events of each type that you saw was close to the number of events of each type that your model predicts will occur on average. You ask, was the final tally of events closer on average to what the model tells us we'd see if no Higgs are being produced? Or is it closer to what the model tells us we'd see if the Higgs was being produced? Or is something else entirely happening?

Standard Model SummaryThe Standard Model (SM) is our current best description of the particles of which matter is made and the forces which govern these particles

SM describes 4 fundamental forces

SM describes 12 elementary particles: 6 kinds of quarks and 6 kinds of leptons (not counting anti-particles)

Particles come in two major categories: hadrons and leptons

Standard Model SummaryUp & down quarks (in the form of neutrons and protons) and electrons are constituents of ordinary matter

Other leptons and particles containing quarks can be produced in cosmic ray showers or in high energy particle accelerators; these particles are all short-lived

Each particle has corresponding antiparticle

Particles in Standard ModelSix leptons are all elementary particles – includes the electron

All other particles (hadrons) are composed of combinations of quarks (6 kinds) – isolated quarks are not permitted

Class of hadrons called baryons composed of 3 quarks – includes proton & neutron

Class of hadrons called mesons composed of 2 quarks (quark + anti-quark)

“Ordinary” matter

Matter & Forces from Standard Model

Hadrons

Matter

Leptons


Forces

Weak EM

StrongGravity

QuarksAnti-Quarks

Proton & neutron in this group

Electron in this group

The Standard Model

EM

Strong

Higgs Boson (gravitron) ?

?

Weak

Standard ModelFour Fundamental Forces

In order of decreasing strength:Strong – binds nucleons Electromagnetic – “opposites attract”Weak – involved in radioactive decay (beta decay)Gravity

Forces arise through exchange of a mediating field particle (a boson)

Standard Model - ForcesNeutrons and protons in nucleus held together by strong force, which has a short range

Strong force able to overcome strong electric repulsion of + charged protons

Electrons attracted to nucleus because of electromagnetic force

Weak force involved in neutron decay – involves changing one type of quark into 2nd type with electron emission

Matter mostly empty space; forces make it seem like it isn’t

The Nucleus

Concentrated positive charge in nucleus

Nucleus should repel and blow apart

But nucleons have a deeper structure

Proton Neutron

Forces In The AtomElectrons held in place by electromagnetic force

Nucleons held together by strong force

Force Carrier Particles (Bosons)

Strong Gluons

Electromagnetic Photons

Gravity Gravitons?

Getting weaker

Proton made of three quarks

One Down Quark

Two Up Quarks

Up quark has charge +2/3 and mass of (approximately) 1/3

Down quark has charge –1/3 and mass of (approximately) 1/3

Mass = 1/3 + 1/3 + 1/3 = 1Charge = 2/3 + 2/3 – 1/3 = +1

The Proton

The Neutron

Neutron also made of three quarks

Two Down Quarks

One Up Quark

Mass = 1/3 + 1/3 + 1/3 = 1

Charge = 2/3 – 1/3 – 1/3 = 0

Neutrons can decay

neutron proton

Beta Decay In Neutron

electron neutrino

W– boson

Example of weak force, of which W– is a boson

Current WorkLarge accelerator experiments at Fermilab (Illinois) and at CERN (Switzerland/France) continuing to search for new particles and test Standard Model predictions

Major hot topics in physics include:

Origin of mass (Higg’s Boson)

Existence of dark matter / dark energy

Acceleration of expansion of universe

Lack of antimatter

Grand unification: theory of gravity + other forces

chapter 4 structure of the atom

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