From the Schr.C3.B6dinger equation to c1 time-dependence Transition of state
1 schrödinger equation c1 time-dependence
1.1 energy operator in schrödinger equation
1.2 unperturbed hamiltonian
1.3 extract c1(t) time dependence
from schrödinger equation c1 time-dependence
the schrödinger equation written :
(
−
ℏ
2
2
m
∂
2
∂
x
2
+
v
(
x
)
)
Ψ
(
x
,
t
)
=
i
ℏ
∂
Ψ
(
x
,
t
)
∂
t
{\displaystyle \left(-{\dfrac {\hbar ^{2}}{2m}}{\dfrac {\partial ^{2}}{\partial x^{2}}}+v(x)\right)\psi (x,t)=i\hbar {\dfrac {\partial \psi (x,t)}{\partial t}}}
energy operator in schrödinger equation
the time derivative in right part of schrödinger equation reads:
i
ℏ
∂
Ψ
(
x
,
t
)
∂
t
=
i
ℏ
(
ψ
0
exp
(
−
i
e
0
t
ℏ
)
(
c
0
′
(
t
)
−
i
e
0
ℏ
c
0
(
t
)
)
+
ψ
1
exp
(
−
i
e
1
t
ℏ
)
(
c
1
′
(
t
)
−
i
e
1
ℏ
c
1
(
t
)
)
)
{\displaystyle i\hbar {\dfrac {\partial \psi (x,t)}{\partial t}}=i\hbar \left(\psi _{0}\exp \left(-i{\dfrac {e_{0}t}{\hbar }}\right)\left({c_{0}} (t)-i{\dfrac {e_{0}}{\hbar }}c_{0}(t)\right)+\psi _{1}\exp \left(-i{\dfrac {e_{1}t}{\hbar }}\right)\left({c_{1}} (t)-i{\dfrac {e_{1}}{\hbar }}c_{1}(t)\right)\right)}
i
ℏ
∂
Ψ
(
x
,
t
)
∂
t
=
i
ℏ
(
Ψ
0
(
c
0
′
(
t
)
−
i
e
0
ℏ
c
0
(
t
)
)
+
Ψ
1
(
c
1
′
(
t
)
−
i
e
1
ℏ
c
1
(
t
)
)
)
{\displaystyle i\hbar {\dfrac {\partial \psi (x,t)}{\partial t}}=i\hbar \left(\psi _{0}\left({c_{0}} (t)-i{\dfrac {e_{0}}{\hbar }}c_{0}(t)\right)+\psi _{1}\left({c_{1}} (t)-i{\dfrac {e_{1}}{\hbar }}c_{1}(t)\right)\right)}
unperturbed hamiltonian
on right part, total hamiltonian sum of unperturbed hamiltonian (without external electric field) , external perturbation. allows substitute eigenvalues of stationary states in total hamiltonian. write:
h
^
Ψ
(
x
,
t
)
=
(
e
0
c
0
(
t
)
Ψ
0
(
x
,
t
)
+
e
1
c
1
(
t
)
Ψ
1
(
x
,
t
)
+
e
ϵ
(
t
)
x
Ψ
(
x
,
t
)
)
{\displaystyle {\hat {h}}\psi (x,t)=\left(e_{0}c_{0}(t)\psi _{0}(x,t)+e_{1}c_{1}(t)\psi _{1}(x,t)+e\epsilon (t)x\psi (x,t)\right)}
using schrödinger equation above, end with
e
ϵ
(
t
)
x
Ψ
(
x
,
t
)
=
i
ℏ
(
c
1
′
(
t
)
Ψ
1
(
x
,
t
)
+
c
0
′
(
t
)
Ψ
0
(
x
,
t
)
)
{\displaystyle e\epsilon (t)x\psi (x,t)=i\hbar (c_{1} (t)\psi _{1}(x,t)+c_{0} (t)\psi _{0}(x,t))}
extract c1(t) time dependence
we use bra–ket notation avoid cumbersome integrals. reads :
e
ϵ
(
t
)
(
c
1
(
t
)
x
|
Ψ
1
(
x
,
t
)
⟩
+
c
0
(
t
)
x
|
Ψ
0
(
x
,
t
)
⟩
=
i
ℏ
(
c
1
′
(
t
)
|
Ψ
1
(
x
,
t
)
⟩
+
c
0
′
(
t
)
x
|
Ψ
0
(
x
,
t
)
⟩
)
{\displaystyle e\epsilon (t)(c_{1}(t)x|\psi _{1}(x,t)\rangle +c_{0}(t)x|\psi _{0}(x,t)\rangle =i\hbar (c_{1} (t)|\psi _{1}(x,t)\rangle +c_{0} (t)x|\psi _{0}(x,t)\rangle )}
then multiply
⟨
Ψ
1
|
{\displaystyle \langle \psi _{1}|}
, end following
e
ϵ
(
t
)
(
c
1
(
t
)
⟨
Ψ
1
|
x
|
Ψ
1
⟩
+
c
0
(
t
)
⟨
Ψ
1
|
x
|
Ψ
0
⟩
)
=
i
ℏ
(
c
1
′
(
t
)
⟨
Ψ
1
|
Ψ
1
⟩
+
c
0
′
(
t
)
⟨
Ψ
1
|
Ψ
0
⟩
)
{\displaystyle e\epsilon (t)(c_{1}(t)\langle \psi _{1}|x|\psi _{1}\rangle +c_{0}(t)\langle \psi _{1}|x|\psi _{0}\rangle )=i\hbar \left(c_{1} (t)\langle \psi _{1}|\psi _{1}\rangle +c_{0} (t)\langle \psi _{1}|\psi _{0}\rangle \right)}
the 2 different levels orthogonal,
⟨
Ψ
1
|
Ψ
0
⟩
=
0
{\displaystyle \langle \psi _{1}|\psi _{0}\rangle =0}
. working normalized wave functions,
⟨
Ψ
1
|
Ψ
1
⟩
=
1
{\displaystyle \langle \psi _{1}|\psi _{1}\rangle =1}
.
finally,
e
ϵ
(
t
)
(
c
1
(
t
)
⟨
Ψ
1
|
x
|
Ψ
1
⟩
+
c
0
(
t
)
⟨
Ψ
1
|
x
|
Ψ
0
⟩
)
=
i
ℏ
c
1
′
(
t
)
{\displaystyle e\epsilon (t)\left(c_{1}(t)\langle \psi _{1}|x|\psi _{1}\rangle +c_{0}(t)\langle \psi _{1}|x|\psi _{0}\rangle \right)=i\hbar c_{1} (t)}
this latter equation expresses time variation of c1 time. crux of our calculation, since then, can deduce expression differential equation obtained.
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