The Pauli Exclusion Principle and Energy Conservation for Bound
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Lecture #2: August 25, 2020 Goal Is to Define Electrons in Atoms
Lecture #2: August 25, 2020 Goal is to define electrons in atoms • Bohr Atom and Principal Energy Levels from “orbits”; Balance of electrostatic attraction and centripetal force: classical mechanics • Inability to account for emission lines => particle/wave description of atom and application of wave mechanics • Solutions of Schrodinger’s equation, Hψ = Eψ Required boundaries => quantum numbers (and the Pauli Exclusion Principle) • Electron configurations. C: 1s2 2s2 2p2 or [He]2s2 2p2 Na: 1s2 2s2 2p6 3s1 or [Ne] 3s1 => Na+: [Ne] Cl: 1s2 2s2 2p6 3s23p5 or [Ne]3s23p5 => Cl-: [Ne]3s23p6 or [Ar] What you already know: Quantum Numbers: n, l, ml , ms n is the principal quantum number, indicates the size of the orbital, has all positive integer values of 1 to ∞(infinity) (Bohr’s discrete orbits) l (angular momentum) orbital 0s l is the angular momentum quantum number, 1p represents the shape of the orbital, has integer values of (n – 1) to 0 2d 3f ml is the magnetic quantum number, represents the spatial direction of the orbital, can have integer values of -l to 0 to l Other terms: electron configuration, noble gas configuration, valence shell ms is the spin quantum number, has little physical meaning, can have values of either +1/2 or -1/2 Pauli Exclusion principle: no two electrons can have all four of the same quantum numbers in the same atom (Every electron has a unique set.) Hund’s Rule: when electrons are placed in a set of degenerate orbitals, the ground state has as many electrons as possible in different orbitals, and with parallel spin. -
Solving the Schrödinger Equation for Helium Atom and Its Isoelectronic
THE JOURNAL OF CHEMICAL PHYSICS 127, 224104 ͑2007͒ Solving the Schrödinger equation for helium atom and its isoelectronic ions with the free iterative complement interaction „ICI… method ͒ Hiroyuki Nakashima and Hiroshi Nakatsujia Quantum Chemistry Research Institute, Kyodai Katsura Venture Plaza 106, Goryo Oohara 1-36, Nishikyo-ku, Kyoto 615-8245, Japan and Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Nishikyo-ku, Kyoto 615-8510, Japan ͑Received 31 July 2007; accepted 2 October 2007; published online 11 December 2007͒ The Schrödinger equation was solved very accurately for helium atom and its isoelectronic ions ͑Z=1–10͒ with the free iterative complement interaction ͑ICI͒ method followed by the variational principle. We obtained highly accurate wave functions and energies of helium atom and its isoelectronic ions. For helium, the calculated energy was −2.903 724 377 034 119 598 311 159 245 194 404 446 696 905 37 a.u., correct over 40 digit accuracy, and for H−,itwas−0.527 751 016 544 377 196 590 814 566 747 511 383 045 02 a.u. These results prove numerically that with the free ICI method, we can calculate the solutions of the Schrödinger equation as accurately as one desires. We examined several types of scaling function g and initial function 0 of the free ICI method. The performance was good when logarithm functions were used in the initial function because the logarithm function is physically essential for three-particle collision area. The best performance was obtained when we introduce a new logarithm function containing not only r1 and r2 but also r12 in the same logarithm function. -
Many-Electron System I – Helium Atom and Pauli Exclusion Principle
Lecture 17 Many-electron System I { Helium Atom and Pauli Exclusion Principle Study Goal of This Lecture • Helium atom - many electron wavefunctions • Helium atom - variational ground state (screening) • Eigenstates of a two-spin system 17.1 Helium Atom Helium atom includes two electrons moving around a fixed nucleus with charge Z = 2, we can write down the Hamiltonian as: 2 2 2 2 ^ ~ 2 2 1 Ze Ze e H = − (r1 + r2) − ( + − ) 2me 4π0 r1 r2 r12 2 2 2 2 2 ~ 2 1 Ze ~ 2 1 Ze e = − r1 − − − r2 − + 2me 4π0 r1 2me 4π0 r2 4π0r12 (17.1) | {z } | {z } | {z } H^1 H^2 H^12 = H^1 + H^2 + H^12: 1 If H^12 = 0(or neglected) then the problem is exactly solved. Recall that for a total system composes of independent sub-systems H^T = H^1 + H^2 + ··· ; (17.2) and we can firstly solve all ^ n n n Hnφm = Emφm; (17.3) then the solution of H^T is the product states Y n = φ : (17.4) n If consider as many-electrons, i.e. H^n for the n-th electron. Then the product solu- tion is a natural "independent electron" solution. Even when the electron-electron interactions are non-zero, we will see the independent electorn approximation is a good starting point. Let's consider the Helium atom, we know: H^1φ1 = E1φ1; (17.5) H^2φ2 = E2φ2; and total E = E1 + E2. φ1; φ2 are Helium hydrogen-like atomic orbitals. We know the two ground states (neglect spin for a moment.) H^1φ1s(1) = E1sφ1s(1); (17.6) H^2φ1s(2) = E1sφ1s(2); number 1 and 2 denotes electorn 1 and electron 2 respectively. -
The Quantum Mechanical Model of the Atom
The Quantum Mechanical Model of the Atom Quantum Numbers In order to describe the probable location of electrons, they are assigned four numbers called quantum numbers. The quantum numbers of an electron are kind of like the electron’s “address”. No two electrons can be described by the exact same four quantum numbers. This is called The Pauli Exclusion Principle. • Principle quantum number: The principle quantum number describes which orbit the electron is in and therefore how much energy the electron has. - it is symbolized by the letter n. - positive whole numbers are assigned (not including 0): n=1, n=2, n=3 , etc - the higher the number, the further the orbit from the nucleus - the higher the number, the more energy the electron has (this is sort of like Bohr’s energy levels) - the orbits (energy levels) are also called shells • Angular momentum (azimuthal) quantum number: The azimuthal quantum number describes the sublevels (subshells) that occur in each of the levels (shells) described above. - it is symbolized by the letter l - positive whole number values including 0 are assigned: l = 0, l = 1, l = 2, etc. - each number represents the shape of a subshell: l = 0, represents an s subshell l = 1, represents a p subshell l = 2, represents a d subshell l = 3, represents an f subshell - the higher the number, the more complex the shape of the subshell. The picture below shows the shape of the s and p subshells: (notice the electron clouds) • Magnetic quantum number: All of the subshells described above (except s) have more than one orientation. -
Helium Atom, Approximate Methods
Helium Atom, Approximate Methods 22nd April 2008 I. The Helium Atom and Variational Principle: Approximation Methods for Complex Atomic Systems The hydrogen atom wavefunctions and energies, we have seen, are deter- mined as a combination of the various quantum "dynamical" analogues of classical motions (translation, vibration, rotation) and a central-force inter- action (i.e, the Coulomb interaction between an electron and a nucleus). Now, we consider the Helium atom and will see that due to the attendant 3-body problem for which we cannot determine a close-for, first-principles analytic solution, we will have to find recourse in approximate methods. The Helium atom has 2 electrons with coordinates r1 and r2 as well as a single nucleus with coordinate R. The nuclues carries a Z = +2e charge. The Schrodinger equation is: 2 2 2 h¯ 2 h¯ 2 h¯ 2 1 2 (R; r1; r2) + −2M r − 2me r − 2me r ! 2e2 2e2 e2 + (R; r ; r ) = E (R; r ; r ) −4π R r − 4π R r 4π r r 1 2 1 2 o j − 1j o j − 2j o j 1 − 2j! where the symbol "nabla", when squared, is given by: @2 @2 @2 2 = + + r @x2 @y2 @z2 Keep in mind that the R, r, and r represent the Cartesian coordinates of each paticle. This is a 3-body problem and such problems are not solved exactly. Thus, the problem will be reformulated in terms of 2 variables. The first approximations: Mme , fix the nucleous at the origin (R) = 0. Thus, the Schrodinger equation in relative variables is: 1 2 2 2 h¯ 2 2 2e 1 1 e 1 2 (r1; r2) + + (r1; r2) = E (r1; r2) 2me −∇ − r −4πo r1 r2 4πo r2 r1 j − j Recall that the 2, representing the kinetic energy operator, in spherical r polar coordinates is: 1 @ @ 1 @ @ 1 @2 r2 + sinθ + 2 @r 1 @r 2 @θ 1 @θ 2 2 2 r1 1 1 r1sinθ1 1 1 r1sin θ1 @φ1 The Independent Electron Approximation to Solving the Helium Atom Schrodinger Equation If we neglect electron-electron repulsion in the Helium atom problem, we can simplify and solve the effective 2-body problem. -
Quantum Spin Systems and Their Local and Long-Time Properties Carolee Wheeler Faculty Advisor: Robert Sims
URA Project Proposal Quantum Spin Systems and Their Local and Long-Time Properties Carolee Wheeler Faculty Advisor: Robert Sims In quantum mechanics, spin is an important concept having to do with atomic nuclei, hadrons, and elementary particles. Spin may be thought of as a measure of a particle’s rotation about its axis. However, spin differs from orbital angular momentum in the sense that the particles may carry integer or half-integer quantum numbers, i.e. 0, 1/2, 1, 3/2, 2, etc., whereas orbital angular momentum may only take integer quantum numbers. Furthermore, the spin of a charged elementary particle is related to a magnetic dipole moment. All quantum mechanic particles have an inherent spin. This is due to the fact that elementary particles (such as photons, electrons, or quarks) cannot be divided into smaller entities. In other words, they cannot be viewed as particles that are made up of individual, smaller particles that rotate around a common center. Thus, the spin that elementary particles carry is an intrinsic property [1]. An important characteristic of spin in quantum mechanics is that it is quantized. The magnitude of spin takes values S = h s(s + )1 , with h being the reduced Planck’s constant and s being the spin quantum number (a non- negative integer or half-integer). Spin may also be viewed in composite particles, and is calculated by summing the spins of the constituent particles. In the case of atoms and molecules, spin is the sum of the spins of unpaired electrons [1]. Particles with spin can possess a magnetic moment. -
The Principal Quantum Number the Azimuthal Quantum Number The
To completely describe an electron in an atom, four quantum numbers are needed: energy (n), angular momentum (ℓ), magnetic moment (mℓ), and spin (ms). The Principal Quantum Number This quantum number describes the electron shell or energy level of an atom. The value of n ranges from 1 to the shell containing the outermost electron of that atom. For example, in caesium (Cs), the outermost valence electron is in the shell with energy level 6, so an electron incaesium can have an n value from 1 to 6. For particles in a time-independent potential, as per the Schrödinger equation, it also labels the nth eigen value of Hamiltonian (H). This number has a dependence only on the distance between the electron and the nucleus (i.e. the radial coordinate r). The average distance increases with n, thus quantum states with different principal quantum numbers are said to belong to different shells. The Azimuthal Quantum Number The angular or orbital quantum number, describes the sub-shell and gives the magnitude of the orbital angular momentum through the relation. ℓ = 0 is called an s orbital, ℓ = 1 a p orbital, ℓ = 2 a d orbital, and ℓ = 3 an f orbital. The value of ℓ ranges from 0 to n − 1 because the first p orbital (ℓ = 1) appears in the second electron shell (n = 2), the first d orbital (ℓ = 2) appears in the third shell (n = 3), and so on. This quantum number specifies the shape of an atomic orbital and strongly influences chemical bonds and bond angles. -
Quantum Physics (UCSD Physics 130)
Quantum Physics (UCSD Physics 130) April 2, 2003 2 Contents 1 Course Summary 17 1.1 Problems with Classical Physics . .... 17 1.2 ThoughtExperimentsonDiffraction . ..... 17 1.3 Probability Amplitudes . 17 1.4 WavePacketsandUncertainty . ..... 18 1.5 Operators........................................ .. 19 1.6 ExpectationValues .................................. .. 19 1.7 Commutators ...................................... 20 1.8 TheSchr¨odingerEquation .. .. .. .. .. .. .. .. .. .. .. .. .... 20 1.9 Eigenfunctions, Eigenvalues and Vector Spaces . ......... 20 1.10 AParticleinaBox .................................... 22 1.11 Piecewise Constant Potentials in One Dimension . ...... 22 1.12 The Harmonic Oscillator in One Dimension . ... 24 1.13 Delta Function Potentials in One Dimension . .... 24 1.14 Harmonic Oscillator Solution with Operators . ...... 25 1.15 MoreFunwithOperators. .. .. .. .. .. .. .. .. .. .. .. .. .... 26 1.16 Two Particles in 3 Dimensions . .. 27 1.17 IdenticalParticles ................................. .... 28 1.18 Some 3D Problems Separable in Cartesian Coordinates . ........ 28 1.19 AngularMomentum.................................. .. 29 1.20 Solutions to the Radial Equation for Constant Potentials . .......... 30 1.21 Hydrogen........................................ .. 30 1.22 Solution of the 3D HO Problem in Spherical Coordinates . ....... 31 1.23 Matrix Representation of Operators and States . ........... 31 1.24 A Study of ℓ =1OperatorsandEigenfunctions . 32 1.25 Spin1/2andother2StateSystems . ...... 33 1.26 Quantum -
HELIUM ATOM R R2 R1 R2 R1
HELIUM ATOM Now that we have treated the Hydrogen like atoms in some detail, we now proceed to discuss the nextsimplest system: the Helium atom. In this situation, we have tow electrons – with coordinates z r1 and r2 – orbiting a nucleus with charge Z = 2 located at the point R. Now, for the hydrogen atom we were able to ignore the motion of the nucleus r2 by transforming to the center of mass. We then obtained a Schrödinger equation for a single R y effective particle – with a reduced mass that was very close to the electron mass – orbiting the x origin. It turns out to be fairly difficult to r1 transform to the center of mass when dealing with three particles, as is the case for Helium. However, because the nucleus is much more massive than either of the two electrons (MNuc ≈ 7000 mel) it is a very good z approximation to assume that the nucleus sits at the center of mass of the atom. In this approximate set of COM coordinates, then, R=0 r2 and the electron coordinates r and r measure 1 2 y the between each electron and the nucleus. Further, we feel justified in separating the motion of the nucleus (which will roughly x r correspond to rigidly translating the COM of the 1 atom) from the relative d the electrons orbiting the nucleus within the COM frame. Thus, in what follows, we focus only on the motion of the electrons and ignore the motion of the nucleus. We will treat the quantum mechanics of multiple particles (1,2,3…) in much the same way as we described multiple dimensions. -
Chem 1A Chapter 7 Exercises
Chem 1A Chapter 7 Exercises Exercises #1 Characteristics of Waves 1. Consider a wave with a wavelength = 2.5 cm traveling at a speed of 15 m/s. (a) How long does it take for the wave to travel a distance of one wavelength? (b) How many wavelengths (or cycles) are completed in 1 second? (The number of waves or cycles completed per second is referred to as the wave frequency.) (c) If = 3.0 cm but the speed remains the same, how many wavelengths (or cycles) are completed in 1 second? (d) If = 1.5 cm and the speed remains the same, how many wavelengths (or cycles) are completed in 1 second? (e) What can you conclude regarding the relationship between wavelength and number of cycles traveled in one second, which is also known as frequency ()? Answer: (a) 1.7 x 10–3 s; (b) 600/s; (c) 500/s; (d) 1000/s; (e) ?) 2. Consider a red light with = 750 nm and a green light = 550 nm (a) Which light travels a greater distance in 1 second, red light or green light? Explain. (b) Which light (red or green) has the greater frequency (that is, contains more waves completed in 1 second)? Explain. (c) What are the frequencies of the red and green light, respectively? (d) If light energy is defined by the quantum formula, such that Ep = h, which light carries more energy per photon? Explain. 8 -34 (e) Assuming that the speed of light, c = 2.9979 x 10 m/s, Planck’s constant, h = 6.626 x 10 J.s., and 23 Avogadro’s number, NA = 6.022 x 10 /mol, calculate the energy: (i) per photon; (ii) per mole of photon for green and red light, respectively. -
Comparing Many-Body Approaches Against the Helium Atom Exact Solution
SciPost Phys. 6, 040 (2019) Comparing many-body approaches against the helium atom exact solution Jing Li1,2, N. D. Drummond3, Peter Schuck1,4,5 and Valerio Olevano1,2,6? 1 Université Grenoble Alpes, 38000 Grenoble, France 2 CNRS, Institut Néel, 38042 Grenoble, France 3 Department of Physics, Lancaster University, Lancaster LA1 4YB, United Kingdom 4 CNRS, LPMMC, 38042 Grenoble, France 5 CNRS, Institut de Physique Nucléaire, IN2P3, Université Paris-Sud, 91406 Orsay, France 6 European Theoretical Spectroscopy Facility (ETSF) ? [email protected] Abstract Over time, many different theories and approaches have been developed to tackle the many-body problem in quantum chemistry, condensed-matter physics, and nuclear physics. Here we use the helium atom, a real system rather than a model, and we use the exact solution of its Schrödinger equation as a benchmark for comparison between methods. We present new results beyond the random-phase approximation (RPA) from a renormalized RPA (r-RPA) in the framework of the self-consistent RPA (SCRPA) originally developed in nuclear physics, and compare them with various other approaches like configuration interaction (CI), quantum Monte Carlo (QMC), time-dependent density- functional theory (TDDFT), and the Bethe-Salpeter equation on top of the GW approx- imation. Most of the calculations are consistently done on the same footing, e.g. using the same basis set, in an effort for a most faithful comparison between methods. Copyright J. Li et al. Received 15-01-2019 This work is licensed under the Creative Commons Accepted 21-03-2019 Check for Attribution 4.0 International License. -
INTRODUCTION to CARBON-13 NMR the Following Table Shows The
INTRODUCTION TO CARBON-13 NMR The following table shows the spin quantum numbers of several nuclei. Only elements that have a nuclear spin quantum number I other than zero are NMR active. Such elements have odd atomic number, or odd atomic mass, or both. Elements whose atomic number and atomic mass are both even have I = 0 and are not NMR active. SPIN QUANTUM NUMBERS OF COMMON NUCLEI 1 2 12 13 14 16 17 19 31 35 1H 1H 6C 6C 7N 8O 8O 9F 15P 17Cl Nuclear spin quantum 1/2 1 0 1/2 1 0 5/2 1/2 1/2 3/2 number (I) Number of spin states 2 3 0 2 3 0 6 2 2 4 n = 2I + 1 Because both proton and carbon have the same nuclear spin value, they behave similarly in NMR and simi- lar guidelines apply to the analysis of their spectra. However, there are also some important differences. Examination of the following table reveals the basis for some of those differences. FIELD STRENGTHS AND RESONANCE FREQUENCIES FOR SELECTED NUCLEI Natural Abundance Field Strength (B ) Absorption Frequency (n) Isotope o (%) in Tesla* in MHz 1.00 42.6 2.35 100 1H 99.98 4.70 200 7.05 300 2H 0.02 1.00 6.5 1.00 10.7 2.35 25 13C 1.11 4.70 50 7.05 75 19F 100 1.00 40 31P 100 1.00 17 *1 Tesla = 10,000 Gauss Natural abundance effect. The natural abundance of proton means that virtually all the hydrogen atoms in a molecule are the 1H isotope, and therefore are in high abundance.