6'
→
j
=
(
e
ℏ
/
2
i
m
)
(
ψ
⋆
g
r
a
d
ψ
−
ψ
g
r
a
d
ψ
⋆
)
.
j
→
=
(
e
ℏ
/
2
i
m
)
(
ψ
⋆
g
r
a
d
ψ
−
ψ
g
r
a
d
ψ
⋆
)
.