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Quantum Mechanics: Eigenfunctions and Operators
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Quantum Mechanics: Eigenfunctions and Operators

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Questions and Answers

What are the values of ψ that correspond to definite values of energy called?

  • Wave function
  • Eigen energy
  • Eigen value
  • Eigen function (correct)
  • What is the condition for two wave functions to be orthogonal?

  • ∫ ψ₁ * ψ₂ dτ = 0 (correct)
  • ∫ ψ₁ * ψ₂ dτ = 1
  • ∫ ψ₁ * ψ₂ dτ = 2
  • ∫ ψ₁ * ψ₂ dτ = -1
  • What does ψ² represent in the context of wave functions?

  • Velocity of the electron
  • Mathematical significance of wave function
  • Energy level of the wave function
  • Probability of finding an electron (correct)
  • What is needed for a wave function to be considered normalized?

    <p>Integration of J² over infinite limits equals one</p> Signup and view all the answers

    What is the integral condition satisfied by complex conjugates of wave functions?

    <p>∫ ψ₁ * ψ₂' dτ = 0</p> Signup and view all the answers

    What is the potential energy inside the box for a particle in a one-dimensional box?

    <p>Zero</p> Signup and view all the answers

    What is the potential energy outside the box when x=0 or x=a?

    <p>Infinity</p> Signup and view all the answers

    Which equation represents the 3D Schrödinger equation for a particle in a box?

    <p>$ rac{d^2ψ}{dx^2} + rac{d^2ψ}{dy^2} + rac{d^2ψ}{dz^2} + rac{8π^2m}{h^2}(E-V)ψ = 0$</p> Signup and view all the answers

    What happens to the wave function (ψ) outside the box when potential energy V is infinity?

    <p>ψ equals zero</p> Signup and view all the answers

    During collisions with the walls of the box, what happens to the energy of the particle?

    <p>There is no energy change</p> Signup and view all the answers

    Study Notes

    Eigenfunctions and Operators

    • Eigenfunctions (ψ) represent wave solutions to the wave equation for specific energy values.
    • An operator is defined by the equation A f(x) = a f(x), indicating a functional relationship where the action of operator A on f(x) results in the scalar multiple a f(x).

    Normalization and Orthogonalization

    • A wave function is normalized if the integral of the probability density (Ψ^2) over all space equals one.
    • Two wavefunctions ψ₁ and ψ₂ are orthogonal if their integral product over all space is zero: ∫ ψ₁ * ψ₂' dτ = 0.

    Significance of Wave Function

    • The wave function ψ has mathematical significance without direct physical interpretation.
    • ψ² represents the probability density of finding an electron at a location in space.

    Particle in One-Dimensional Box

    • The potential energy outside the box is infinite, while inside, it is zero.
    • When confined in a box from x=0 to x=a, (V = ∞) (outside) and (V = 0) (inside).

    Three-Dimensional Schrödinger Equation

    • The general form: ( \frac{d^2ψ}{dx^2} + \frac{d^2ψ}{dy^2} + \frac{d^2ψ}{dz^2} + \frac{8π^2m}{h^2}(E-V)ψ = 0 ).
    • Outside the box, the equation restricts ψ by ( \frac{d^2ψ}{dx^2} - ∞ψ = 0 ).

    Conditions Inside the Box

    • The differential equation inside the box simplifies to ( \frac{d^2ψ}{dx^2} + \frac{8πmE}{h^2}ψ = 0).
    • Parameters will relate to boundary conditions.

    Boundary Conditions

    • For the boundary conditions (y = Asinkx), integration establishes conditions at x=0 and x=a.
    • Solutions yield quantized energy levels defined by (E = \frac{n^2h^2}{8ma^2}).

    Quantum Mechanics and Energy Levels

    • The system's quantum numbers determine energy levels, with (HOMO) being the highest occupied and (LOMO) as the lowest unoccupied molecular orbital.
    • Energy levels can be derived using (E_n) formulas for various n values (n=1,2,3...).

    Molecular Structures and Bond Length

    • Distance measurements: C-C bond length (154 pm), C=C bond length (134 pm).
    • For conjugated systems like CH₂=CH-CH=..., calculations determine energy distribution and bond lengths using given formulas.

    Energy Calculations in Molecules

    • Energy levels for CH₂=CH-CH=CH=CH₂ based on the quantum mechanically derived equation (E_n = \frac{n^2h^2}{8ma^2}).
    • Diagrammatic representation of energy transitions within established energy levels, indicating electron movements.

    Summary of HOMO and LUMO

    • HOMO corresponds to n=2, while LUMO includes the next excited state n=3.
    • Energy gaps between HOMO and LUMO calculated through transitions using derived equations, demonstrating quantum behavior in molecular systems.

    Concept of Nuclear Charge

    • Nuclear charge is denoted by (ze) where (e) represents an electron current in molecular configurations.

    Conjugate Molecule Definition

    • A conjugated molecule has overlapping p-orbitals from adjacent atoms, leading to delocalized π electrons, affecting chemical reactivity and stability.

    Calculations for 2n-e System

    • Energy levels derived from the equation (E_n) lead to reasoning about molecular transitions and energy states visually represented in diagrams.

    Important equations summarizing characteristics

    • Energy states: (E = \frac{(n + \frac{1}{2})^2 h^2}{8\pi^2 a m}) and wave functions contributing to analysis of molecular behavior.

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    Description

    This quiz delves into the fundamental concepts of quantum mechanics, focusing on eigenfunctions and operators. It explores their mathematical significance, normalization, orthogonalization, and the behavior of particles in a one-dimensional box. Test your understanding of these core principles in quantum physics.

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