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Some problems still need clarification. I will update them once we ask professor Cory. |
Dynamics
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| Wiki Markup |
{note:title=Be Careful} Some problems still need clarification. I will update them once we ask professor Cory. {note} h2. Dynamics \\ {latex} $s(t)=e^{-t/T_{2}}\int P(r)e^{-i\int^{t}_{0}\omega(r,t')dt'}dr$ {latex} \\ |
ω(r,t')
...
=
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resonant
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frequency
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P(r)
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=
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probability
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distribution
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- Coherent
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- -
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- when
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- ω
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- is
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- not
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- a
...
- function
...
- of
...
- r
...
- (There
...
- are
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- no
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- interesting
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- dynamics)
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- Stationary
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- -
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- when
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- ω
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- is
...
- not
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- a
...
- function
...
- of
...
- time
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- (the
...
- system
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- can
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- be
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- refocused
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- by
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- a
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- π
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- pulse
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- for
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- any
...
- time)
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- Incoherent
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- -
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- stationary
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- and
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- not
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- coherent,
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- explicitly
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- ω
...
- is
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- a
...
- function
...
- of
...
- r
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- (interesting
...
- question
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- is
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- the
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- distribution
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- of
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- ω(r)
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- Decoherent
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- -
...
- when
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- ω
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- is
...
- a
...
- function
...
- of
...
- time
...
- and
...
- r,
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- and
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- the
...
- t
...
- dependence
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- is
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- stochastic/Marchovian
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- (interesting
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- dynamics:
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- distribution
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- of
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- ω(r),
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- spectral
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- density
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- of
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- ω(r)
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- Periodic
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- -
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- ω
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- is
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- a
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- simple
...
- function
...
- of
...
- time
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- (interesting
...
- dynamics:
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- distribution
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- of
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- ω(r)
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- at
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- the
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- characteristic
...
- frequency)
Periodic
Frequency that an arbitrary location will see
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\\
h3. Periodic
!p1.jpg!
!p2.jpg!
Frequency that an arbitrary location will see
\\
{latex}
$\omega(t) = \gamma r \frac{\partial B_{z}}{\partial x} cos(\omega _{s} t + \phi)$
|
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{latex} \\ {latex} $exp(i\int^{t}_{0}\omega(t')dt'=exp(i[\gamma \frac{\partial B_{z}/\partial x}{\omega_{s}}r sin(\omega_{s}t+\phi])$ {latex} \\ {latex} |
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$exp^{iRsin\alpha}=\sum J_{k}(R)e^{ik\alpha}$
{latex}
|
for
...
one
...
location
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in
...
the
...
sample
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Static
...
Spectrum
Problem 1
- Show that for average over φ, we get pure absorptive line-shape,
...
- and
...
- for
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- a
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- particular
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- isochromat,
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- average
...
- over
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- φ
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- in
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- general
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- has
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- dispersive
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- line-shape
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- (Show
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- the
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- response
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- in
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- cylindrical
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- coordinate)
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- Normal
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- shim:
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- x,y
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- (first
...
- order
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- spherical
...
- harmonic).
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- If
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- there
...
- are
...
- terms
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- x^2-y^2,
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- xy,
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- then
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- the
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- sideband
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- will
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- show
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- up
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- at
...
- twice
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- Ω
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- Calculate
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- the
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- FID
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- and
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- the
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- spectrum
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- for
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- rotary
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- vs
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- non-rotary,
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- then
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- plot
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- them
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- on
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- top
...
- of
...
- each other
Nuclear Spin
- Zeeman interaction
- Chemical shift : ppm variation due to chemistry -> transform as a tensor (orientation of the molecule matter)
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other \\ h3. Nuclear Spin - Zeeman interaction - Chemical shift : ppm variation due to chemistry \-> transform as a tensor (orientation of the molecule matter) \\ {latex}$H_{z}=\omega _{0}I_{z}${latex} \\ |
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{latex}$H_{cs}=-\omega _{0}\sigma I_{z}${latex} \\ !p4.jpg! PAS (Principle axis system) = coordinate system |
PAS (Principle axis system) = coordinate system that leave the molecule in diagonal ??
ω in transverse plane (slow) can be suppressed if rotation around z-axis is fast
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that leave the molecule in diagonal ?? !p5.jpg! ω in transverse plane (slow) can be suppressed if rotation around z-axis is fast !p6.jpg!\\ {latex}$\sigma _{z} \sigma _{z}'${latex} |
=
...
secular
...
part
...
of
...
the
...
chemical
...
shift,
...
lead
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to
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small
...
rotation
...
in
...
x-y direction
Problem 2
- Show that chemical shift tensor
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direction
\\
*Problem 2*
- Show that chemical shift tensor
\\
{latex}
$\sigma = \sigma_{iso} + (\frac{\sigma}{2})(3 cos^{2}\theta -1)- \frac{\delta^{eta}}{4}sin^{2}\theta(e^{i2\phi}+e^{-i2\phi})$
|
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{latex} \\ {latex} $\sigma_{iso}=(\sigma_{xx}+\sigma_{yy}+\sigma_{zz})/3$ {latex} \\ {latex |
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} $\delta=\frac{2}{3}\sigma_{zz}-\frac{1}{3}(\sigma_{xx}+\sigma_{yy})$ {latex} \\ {latex} |
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$\eta=3(\sigma_{yy}-\sigma_{xx})/2(\sigma_{zz}-\sigma_{xx}-\sigma_{yy})$
{latex}
\\
- Show that under random rapid motion spins
\\
{ |
- Show that under random rapid motion spins
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latex}$< \sigma > = \sigma _{iso}${latex} \\ It average out any |
It average out any non-isometric
...
parts,
...
so
...
we
...
have
...
a
...
homogeneous
...
sample.
...
So
...
the
...
result
...
does
...
not
...
depend
...
on
...
the
...
orientation
...
of
...
the
...
sample.
...
When
...
η
...
=
...
0
...
->
...
<
...
3cos(θ)^2
...
-1
...
>
...
=
...
0,
...
average
...
over
...
sphere
...
- η
...
- =
...
- 0
...
- ;
...
- calculate
...
- the
...
- line-shape
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- for
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- static
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- powder
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- (constant
...
- orientation
...
- with
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- magnetic
...
- field),
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- η
...
- ≠
...
- 0
...
- ;
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- reduce
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- to
...
- a
...
- summation
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- over
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- η.
...
- [Hint:
...
- can
...
- be
...
- written
...
- in
...
- elliptical
...
- integral,
...
- check
...
- out
...
- appendix
...
- I
...
- ]
- Find σ(θ,φ),
...
- powder
...
- distribution
...
- of
...
- the
...
- sample
...
- (when
...
- spinning
...
- at
...
- the
...
- magic
...
- angle
...
- ?)
Decoherence
Bloc = field that a test spin would see (every spin averagely see the same distribution of B)
average vector still pointing along y => |Bloc> of time or ensemble = 0
Problem 3
- What is the contribution of the chemical shift anisotropy to T2?
Carl-Purcell Sequence
Problem 4
- Look at diffusive attenuation of water rotating in magnetic field gradient. (The faster you rotate it, the effective T2 is approaching T2)
Chemical Exchange
let
Problem 5
- Show the plot of the chemical exchange (when τ|ΔωA-ΔωB| approaching 1, the 2 peaks merge at the center) [Hint: check out appendix F]
Slow Exchange
choose Δ ≥ τ exchange, Δ << T1, Δ > T2
Problem 6
- Show that by collect this terms in slow exchange
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\\
h3. Decoherence
Bloc = field that a test spin would see (every spin averagely see the same distribution of B)
!p7.jpg!
average vector still pointing along y => \|Bloc> of time or ensemble = 0
!eq1.jpg!
!p8.jpg!
!p9.jpg!
*Problem 3*
- What is the contribution of the chemical shift anisotropy to T2?
\\
h3. Carl-Purcell Sequence
!p10.jpg!
!eq2.jpg!
*Problem 4*
- Look at diffusive attenuation of water rotating in magnetic field gradient. (The faster you rotate it, the effective T2 is approaching T2)
\\
h3. Chemical Exchange
let
!eq3.jpg!
!p11.jpg!
*Problem 5*
- Show the plot of the chemical exchange (when τ\|ΔωA-ΔωB\| approaching 1, the 2 peaks merge at the center) \[Hint: check out appendix F\]
\\
h3. Slow Exchange
!p12.jpg!
choose Δ ≥ τ exchange, Δ << T1, Δ > T2
*Problem 6*
- Show that by collect this terms in slow exchange
\\
{latex}
$e^{i\omega_{A}t_{1}}e^{i\omega_{A}t_{2}} , e^{i\omega_{A}t_{1}}e^{i\omega_{B}t_{2}} , e^{i\omega_{B}t_{1}}e^{i\omega_{A}t_{2}} , e^{i\omega_{B}t_{1}}e^{i\omega_{B}t_{2}}$
|
then do phase cycle and collect data set
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{latex} \\ then do phase cycle and collect data set \\ {latex} $cos(\omega_{A/D}T_{1})e^{i\omega_{A/D}t_{2}} , sin(\omega_{A/D}T_{1})e^{i\omega_{A/D}t_{2}}$ {latex} \\ Then we get pure absorptive |
Then we get pure absorptive line-shape