The time-independent Schrödinger equation describes the stationary states of a quantum system. It is written as:
Hψ = Eψ
where:H is the Hamiltonian operator, which represents the total energy of the system.
ψ is the wave function of the system, which describes the state of the system.
E is the energy of the system.
To derive the expression for the time-independent Schrödinger equation, we start with the time-dependent Schrödinger equation:
iħ∂ψ/∂t = Hψ
where:i is the imaginary unit (√(-1)).
ħ is the reduced Planck's constant (h/2π).
∂ψ/∂t is the partial derivative of the wave function with respect to time.
To eliminate the time dependence, we can assume a solution of the form:
ψ(r, t) = Φ(r)T(t)
where:ψ(r, t) is the wave function.
Φ(r) is the spatial part of the wave function, depending only on position.
T(t) is the temporal part of the wave function, depending only on time.
Substituting this into the time-dependent Schrödinger equation, we get:
iħ(Φ(r)dT(t)/dt) = H(Φ(r)T(t))
Dividing through by ψ, we have:
(iħ/Φ(r))dT(t)/dt = (H/Φ(r))T(t)
Since the left side depends only on time (T(t)) and the right side depends only on position (Φ(r)), both sides must be constant. Let's denote this constant as E. Rearranging the equation, we obtain:
(iħ/Φ(r))dT(t)/dt = E
(H/Φ(r))T(t) = E
Now, we have separated the equation into two parts. The first part depends only on time and gives a differential equation for T(t), while the second part depends only on position and gives an eigenvalue equation for Φ(r).
The time part equation is:
(iħ/Φ(r))dT(t)/dt = E
Simplifying, we have:
dT(t)/dt = -(iħ/E)Φ(r)
The position part equation is:
(H/Φ(r))T(t) = E
Multiplying through by Φ(r), we get:
HΦ(r) = EΦ(r)
This is the eigenvalue equation for the spatial part of the wave function. It relates the Hamiltonian operator to the energy eigenvalue E and the spatial wave function Φ(r).
Therefore, the time-independent Schrödinger equation is given by:
HΦ(r) = EΦ(r)
This equation determines the allowed energy states (E) and their corresponding spatial wave functions (Φ(r)) for a given quantum system.
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