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Today’s Outline - February 24, 2015

• Reflectivity papers

• Kinematical diffraction

Homework Assignment #03:Chapter 3: 1, 3, 4, 6, 8due Thursday, February 26, 2015

C. Segre (IIT) PHYS 570 - Fall 2015 February 24, 2015 1 / 17

Layering in liquid films

THEOS, tetrakis(2-ethylhexoxy)silane, a non-polar, roughly sphericalmolecule, was depositedon Si(111) single crystals

Specular reflection mea-surements were made atMRCAT (Sector 10 atAPS)and at X18A (atNSLS).

Deviations from uniform density are used tofit experimental reflectivity

C.-J. Yu et al., “Observation of molecular layering in thin liquid films usingx-ray reflectivity”, Phys. Rev. Lett. 82, 2326–2329 (1999).

The peak below 10A appears in allbut the thickest film and dependson the interactions between filmand substrate.

There are always peaks between10-20A and 20-30A

A broad peak appears at free sur-face indicating that ordering re-quires a hard smooth surface.

Film growth kinetics

Gaussian roughness profilewith a “roughness” expo-nent 0 < h < 1.

As thefilm is grown by vapor de-position, the rms width σ,grows with a “growth ex-ponent” β and the correla-tion length in the plane ofthe surface, ξ evolves withthe “dynamic” scaling ex-ponent, zs = h/β.

g(r) ∝ r2h σ ∝ tβ

ξ ∝ t1/zs 〈h〉 ∝ t

h ≈ 0.33, β ≈ 0.25 for nodiffusion.

Ag/Si films: 10nm (A), 18nm (B),37nm (C), 73nm (D), 150nm (E)

C. Thompson et al., “X-ray-reflectivity study of the growth kinetics of vapor-deposited silver films”, Phys. Rev. B 49, 4902–4907 (1994).

Gaussian roughness profilewith a “roughness” expo-nent 0 < h < 1.

As thefilm is grown by vapor de-position, the rms width σ,grows with a “growth ex-ponent” β and the correla-tion length in the plane ofthe surface, ξ evolves withthe “dynamic” scaling ex-ponent, zs = h/β.

g(r) ∝ r2h

σ ∝ tβ

ξ ∝ t1/zs 〈h〉 ∝ t

Gaussian roughness profilewith a “roughness” expo-nent 0 < h < 1. As thefilm is grown by vapor de-position, the rms width σ,grows with a “growth ex-ponent” β

and the correla-tion length in the plane ofthe surface, ξ evolves withthe “dynamic” scaling ex-ponent, zs = h/β.

g(r) ∝ r2h

σ ∝ tβ

ξ ∝ t1/zs 〈h〉 ∝ t

Gaussian roughness profilewith a “roughness” expo-nent 0 < h < 1. As thefilm is grown by vapor de-position, the rms width σ,grows with a “growth ex-ponent” β

and the correla-tion length in the plane ofthe surface, ξ evolves withthe “dynamic” scaling ex-ponent, zs = h/β.

ξ ∝ t1/zs 〈h〉 ∝ t

Gaussian roughness profilewith a “roughness” expo-nent 0 < h < 1. As thefilm is grown by vapor de-position, the rms width σ,grows with a “growth ex-ponent” β and the correla-tion length in the plane ofthe surface, ξ evolves withthe “dynamic” scaling ex-ponent, zs = h/β.

ξ ∝ t1/zs 〈h〉 ∝ t

ξ ∝ t1/zs

〈h〉 ∝ t

ξ ∝ t1/zs 〈h〉 ∝ t

h can be obtained from thediffuse off-specular reflec-tion which should vary as

I (qz) ∝ σ−2/hq−(3+1/h)z

This gives h = 0.63 but isthis correct?

Measure it directly usingSTM

g(r) = 2σ2[1− e(r/ξ)2h

]h = 0.78, ξ = 23nm,

σ = 3.2nm

Thus zs = h/β = 2.7 and diffraction data confirm ξ = 19.9〈h〉1/2.7 A

I (qz) ∝ σ−2/hq−(3+1/h)z

g(r) = 2σ2[1− e(r/ξ)2h

]h = 0.78, ξ = 23nm,

σ = 3.2nm

I (qz) ∝ σ−2/hq−(3+1/h)z

g(r) = 2σ2[1− e(r/ξ)2h

]h = 0.78, ξ = 23nm,

σ = 3.2nm

I (qz) ∝ σ−2/hq−(3+1/h)z

g(r) = 2σ2[1− e(r/ξ)2h

]h = 0.78, ξ = 23nm,

σ = 3.2nm

I (qz) ∝ σ−2/hq−(3+1/h)z

g(r) = 2σ2[1− e(r/ξ)2h

]h = 0.78, ξ = 23nm,

σ = 3.2nm

I (qz) ∝ σ−2/hq−(3+1/h)z

g(r) = 2σ2[1− e(r/ξ)2h

]h = 0.78, ξ = 23nm,

σ = 3.2nm

I (qz) ∝ σ−2/hq−(3+1/h)z

g(r) = 2σ2[1− e(r/ξ)2h

]h = 0.78, ξ = 23nm,

σ = 3.2nm

I (qz) ∝ σ−2/hq−(3+1/h)z

g(r) = 2σ2[1− e(r/ξ)2h

h = 0.78, ξ = 23nm,

σ = 3.2nm

I (qz) ∝ σ−2/hq−(3+1/h)z

g(r) = 2σ2[1− e(r/ξ)2h

]h = 0.78, ξ = 23nm,

σ = 3.2nm

Thus zs = h/β = 2.7

and diffraction data confirm ξ = 19.9〈h〉1/2.7 A

I (qz) ∝ σ−2/hq−(3+1/h)z

g(r) = 2σ2[1− e(r/ξ)2h

]h = 0.78, ξ = 23nm,

σ = 3.2nm

Thus zs = h/β = 2.7

and diffraction data confirm ξ = 19.9〈h〉1/2.7 A

I (qz) ∝ σ−2/hq−(3+1/h)z

g(r) = 2σ2[1− e(r/ξ)2h

]h = 0.78, ξ = 23nm,

σ = 3.2nm

Liquid metal surfaces

X-ray reflectivity using syn-chrotron radiation has madepossible the study of the sur-face of liquid metals

a liquid can be described ascharged ions in a sea of con-duction electrons

this leads to a well-definedsurface structure as can beseen in liquid gallium

contrast this with the scat-tering from liquid mercury

P. Pershan, “Review of the highlights of x-ray studies of liquid metal surfaces”, J. Appl. Phys. 116, 222201 (2014).

Liquid metal eutectics

High vapor pressure andthermal excitations limit thenumber of pure metals whichcan be studied but alloy eu-tectics provide many possi-bilities

tune x-rays around the Bi ab-sorption edge at 13.42 keVand measure a Bi43Sn57 eu-tectic

surface layer is rich in Bi(95%), second layer is defi-cient (25%), and third layeris rich in Bi (53%) once again

O. Shpyrko et al., “Atomic-scale surface demixing in a eutectic liquidBiSn alloy”, Phys. Rev. Lett. 95, 106103 (2005).

Scattering from two electrons

Consider systems where there is only weak scattering, with no multiplescattering effects. We begin with the scattering of x-rays from twoelectrons.

~Q = (~k − ~k ′)

|~Q| = 2k sin θ =4π

λsin θ

The scattering from the second electron willhave a phase shift of φ = ~Q ·~r .

A(~Q) = −ro(

1 + e i~Q·~r)

I (~Q) = A(~Q)A(~Q)∗ = r2o

(1 + e i

~Q·~r)(

1 + e−i~Q·~r)

= 2r2o

(1 + cos(~Q ·~r)

~Q = (~k − ~k ′)

|~Q| = 2k sin θ =4π

λsin θ

A(~Q) = −ro(

1 + e i~Q·~r)

I (~Q) = A(~Q)A(~Q)∗ = r2o

(1 + e i

~Q·~r)(

1 + e−i~Q·~r)

= 2r2o

(1 + cos(~Q ·~r)

~Q = (~k − ~k ′)

|~Q| = 2k sin θ =4π

λsin θ

A(~Q) = −ro(

1 + e i~Q·~r)

I (~Q) = A(~Q)A(~Q)∗ = r2o

(1 + e i

~Q·~r)(

1 + e−i~Q·~r)

= 2r2o

(1 + cos(~Q ·~r)

~Q = (~k − ~k ′)

|~Q| = 2k sin θ =4π

λsin θ

A(~Q) = −ro(

1 + e i~Q·~r)

I (~Q) = A(~Q)A(~Q)∗ = r2o

(1 + e i

~Q·~r)(

1 + e−i~Q·~r)

= 2r2o

(1 + cos(~Q ·~r)

~Q = (~k − ~k ′)

|~Q| = 2k sin θ =4π

λsin θ

A(~Q) = −ro(

1 + e i~Q·~r)

I (~Q) = A(~Q)A(~Q)∗ = r2o

(1 + e i

~Q·~r)(

1 + e−i~Q·~r)

= 2r2o

(1 + cos(~Q ·~r)

~Q = (~k − ~k ′)

|~Q| = 2k sin θ =4π

λsin θ

A(~Q) = −ro(

1 + e i~Q·~r)

I (~Q) = A(~Q)A(~Q)∗ = r2o

(1 + e i

~Q·~r)(

1 + e−i~Q·~r)

= 2r2o

(1 + cos(~Q ·~r)

~Q = (~k − ~k ′)

|~Q| = 2k sin θ =4π

λsin θ

A(~Q) = −ro(

1 + e i~Q·~r)

I (~Q) = A(~Q)A(~Q)∗ = r2o

(1 + e i

~Q·~r)(

1 + e−i~Q·~r)

= 2r2o

(1 + cos(~Q ·~r)

~Q = (~k − ~k ′)

|~Q| = 2k sin θ =4π

λsin θ

A(~Q) = −ro(

1 + e i~Q·~r)

I (~Q) = A(~Q)A(~Q)∗ = r2o

(1 + e i

~Q·~r)(

1 + e−i~Q·~r)

= 2r2o

(1 + cos(~Q ·~r)

~Q = (~k − ~k ′)

|~Q| = 2k sin θ =4π

λsin θ

A(~Q) = −ro(

1 + e i~Q·~r)

I (~Q) = A(~Q)A(~Q)∗ = r2o

(1 + e i

~Q·~r)(

1 + e−i~Q·~r)

= 2r2o

(1 + cos(~Q ·~r)

)C. Segre (IIT) PHYS 570 - Fall 2015 February 24, 2015 8 / 17

Scattering from many electrons

for many electrons

generalizing to a crystal

A(~Q) = −ro∑j

e i~Q·~rj

A(~Q) = −ro∑N

e i~Q· ~RN

e i~Q·~rj

Since experiments measure I ∝ A2, the phase information is lost. This is aproblem if we don’t know the specific orientation of the scattering systemrelative to the x-ray beam.

We will now look at the consequences of this orientation and generalize tomore than two electrons

for many electrons

A(~Q) = −ro∑j

e i~Q·~rj

A(~Q) = −ro∑N

e i~Q· ~RN

e i~Q·~rj

for many electrons

A(~Q) = −ro∑j

e i~Q·~rj

A(~Q) = −ro∑N

e i~Q· ~RN

e i~Q·~rj

for many electrons

A(~Q) = −ro∑j

e i~Q·~rj

A(~Q) = −ro∑N

e i~Q· ~RN

e i~Q·~rj

for many electrons

A(~Q) = −ro∑j

e i~Q·~rj

A(~Q) = −ro∑N

e i~Q· ~RN

e i~Q·~rj

for many electrons

A(~Q) = −ro∑j

e i~Q·~rj

A(~Q) = −ro∑N

e i~Q· ~RN

e i~Q·~rj

Two electrons — fixed orientation

The expression

I (~Q) = 2r2o

(1 + cos(~Q ·~r)

)assumes that the two electronshave a specific, fixed orienta-tion. In this case the intensityas a function of Q is.

Fixed orientation is not theusual case, particularly for solu-tion and small-angle scattering. 0 0.5 1 1.5 2

Q (units of 2π/r)

nsity (

units o

f r2 o

The expression

I (~Q) = 2r2o

(1 + cos(~Q ·~r)

Fixed orientation is not theusual case, particularly for solu-tion and small-angle scattering.

0 0.5 1 1.5 2

Q (units of 2π/r)

nsity (

units o

f r2 o

The expression

I (~Q) = 2r2o

(1 + cos(~Q ·~r)

Fixed orientation is not theusual case, particularly for solu-tion and small-angle scattering. 0 0.5 1 1.5 2

Q (units of 2π/r)

nsity (

units o

f r2 o

Orientation averaging

A(~Q) = f1 + f2ei ~Q·~r

I (~Q) = f 21 + f 2

2 + f1f2ei ~Q·~r + f1f2e

−i ~Q·~r

⟨I (~Q)

⟩= f 2

1 + f 22 + 2f1f2

⟨e i~Q·~r⟩

∫e iQr cos θ sin θdθdφ∫

sin θdθdφ

4π2π

∫ π

0e iQr cos θ sin θdθ

(− 1

)∫ −iQr

iQrexdx

sin(Qr)

Consider scattering from twoarbitrary electron distribu-tions, f1 and f2. A(~Q), isgiven by

and the intensity, I (~Q), is

if the distance between thescatterers,~r , remains constant(no vibrations) but is allowedto orient randomly in space⟨I (~Q)

⟩= f 2

1 +f 22 +2f1f2

sin(Qr)

A(~Q) = f1 + f2ei ~Q·~r

I (~Q) = f 21 + f 2

2 + f1f2ei ~Q·~r + f1f2e

−i ~Q·~r

⟨I (~Q)

⟩= f 2

1 + f 22 + 2f1f2

⟨e i~Q·~r⟩

sin θdθdφ

4π2π

∫ π

(− 1

)∫ −iQr

iQrexdx

sin(Qr)

⟩= f 2

1 +f 22 +2f1f2

sin(Qr)

A(~Q) = f1 + f2ei ~Q·~r

I (~Q) = f 21 + f 2

2 + f1f2ei ~Q·~r + f1f2e

−i ~Q·~r

⟨I (~Q)

⟩= f 2

1 + f 22 + 2f1f2

⟨e i~Q·~r⟩

sin θdθdφ

4π2π

∫ π

(− 1

)∫ −iQr

iQrexdx

sin(Qr)

⟩= f 2

1 +f 22 +2f1f2

sin(Qr)

A(~Q) = f1 + f2ei ~Q·~r

I (~Q) = f 21 + f 2

2 + f1f2ei ~Q·~r + f1f2e

−i ~Q·~r

⟨I (~Q)

⟩= f 2

1 + f 22 + 2f1f2

⟨e i~Q·~r⟩

sin θdθdφ

4π2π

∫ π

(− 1

)∫ −iQr

iQrexdx

sin(Qr)

⟩= f 2

1 +f 22 +2f1f2

sin(Qr)

A(~Q) = f1 + f2ei ~Q·~r

I (~Q) = f 21 + f 2

2 + f1f2ei ~Q·~r + f1f2e

−i ~Q·~r

⟨I (~Q)

⟩= f 2

1 + f 22 + 2f1f2

⟨e i~Q·~r⟩

sin θdθdφ

4π2π

∫ π

(− 1

)∫ −iQr

iQrexdx

sin(Qr)

if the distance between thescatterers,~r , remains constant(no vibrations) but is allowedto orient randomly in space

⟨I (~Q)

⟩= f 2

1 +f 22 +2f1f2

sin(Qr)

A(~Q) = f1 + f2ei ~Q·~r

I (~Q) = f 21 + f 2

2 + f1f2ei ~Q·~r + f1f2e

−i ~Q·~r

⟨I (~Q)

⟩= f 2

1 + f 22 + 2f1f2

⟨e i~Q·~r⟩

sin θdθdφ

4π2π

∫ π

(− 1

)∫ −iQr

iQrexdx

sin(Qr)

⟨I (~Q)

⟩= f 2

1 +f 22 +2f1f2

sin(Qr)

A(~Q) = f1 + f2ei ~Q·~r

I (~Q) = f 21 + f 2

2 + f1f2ei ~Q·~r + f1f2e

−i ~Q·~r

⟨I (~Q)

⟩= f 2

1 + f 22 + 2f1f2

⟨e i~Q·~r⟩

sin θdθdφ

4π2π

∫ π

(− 1

)∫ −iQr

iQrexdx

sin(Qr)

⟨I (~Q)

⟩= f 2

1 +f 22 +2f1f2

sin(Qr)

A(~Q) = f1 + f2ei ~Q·~r

I (~Q) = f 21 + f 2

2 + f1f2ei ~Q·~r + f1f2e

−i ~Q·~r

⟨I (~Q)

⟩= f 2

1 + f 22 + 2f1f2

⟨e i~Q·~r⟩

sin θdθdφ

4π2π

∫ π

(− 1

)∫ −iQr

iQrexdx

sin(Qr)

⟨I (~Q)

⟩= f 2

1 +f 22 +2f1f2

sin(Qr)

A(~Q) = f1 + f2ei ~Q·~r

I (~Q) = f 21 + f 2

2 + f1f2ei ~Q·~r + f1f2e

−i ~Q·~r

⟨I (~Q)

⟩= f 2

1 + f 22 + 2f1f2

⟨e i~Q·~r⟩

sin θdθdφ

4π2π

∫ π

(− 1

)∫ −iQr

iQrexdx

sin(Qr)

⟨I (~Q)

⟩= f 2

1 +f 22 +2f1f2

sin(Qr)

A(~Q) = f1 + f2ei ~Q·~r

I (~Q) = f 21 + f 2

2 + f1f2ei ~Q·~r + f1f2e

−i ~Q·~r

⟨I (~Q)

⟩= f 2

1 + f 22 + 2f1f2

⟨e i~Q·~r⟩

sin θdθdφ

4π2π

∫ π

(− 1

)∫ −iQr

iQrexdx

sin(Qr)

=sin(Qr)

⟨I (~Q)

⟩= f 2

1 +f 22 +2f1f2

sin(Qr)

A(~Q) = f1 + f2ei ~Q·~r

I (~Q) = f 21 + f 2

2 + f1f2ei ~Q·~r + f1f2e

−i ~Q·~r

⟨I (~Q)

⟩= f 2

1 + f 22 + 2f1f2

⟨e i~Q·~r⟩

sin θdθdφ

4π2π

∫ π

(− 1

)∫ −iQr

iQrexdx

sin(Qr)

⟨I (~Q)

⟩= f 2

1 +f 22 +2f1f2

sin(Qr)

A(~Q) = f1 + f2ei ~Q·~r

I (~Q) = f 21 + f 2

2 + f1f2ei ~Q·~r + f1f2e

−i ~Q·~r

⟨I (~Q)

⟩= f 2

1 + f 22 + 2f1f2

⟨e i~Q·~r⟩

sin θdθdφ

4π2π

∫ π

(− 1

)∫ −iQr

iQrexdx

sin(Qr)

⟩= f 2

1 +f 22 +2f1f2

sin(Qr)

Randomly oriented electrons

Recall that when we had a fixedorientation of the two electrons,we had and intensity variation ascos(Qr).

When we now replace the twoarbitrary scattering distributionswith electrons (f1, f2 → −ro),we change the intensity profilesignificantly.

0 0.5 1 1.5 2

Q (units of 2π/r)

nsity (

units o

f r2 o

0 0.5 1 1.5 2

Q (units of 2π/r)

nsity (

units o

f r2 o

0 0.5 1 1.5 2

Q (units of 2π/r)

nsity (

units o

f r2 o

Hydrogen form factor calculation

Since ρ(r) = |ψ1s(r)|2, the form factor integral becomes

f 01s(~Q) =

∫e−2r/ae i

~Q·~r r2 sin θdrdθdφ

the integral in φ gives 2π and if we choose ~Q to be along the z direction,~Q ·~r → Qr cos θ, so

f 01s(~Q) =

∫ ∞0

2πr2e−2r/a

∫ π

0e iQr cos θ sin θdθdr

∫ ∞0

2πr2e−2r/a 1

[−e iQr cos θ

∣∣∣π0dr

∫ ∞0

2πr2e−2r/a 1

[e iQr − e−iQr

∫ ∞0

2πr2e−2r/a 2 sin(Qr)

f 01s(~Q) =

∫e−2r/ae i

f 01s(~Q) =

∫ ∞0

2πr2e−2r/a

∫ π

∫ ∞0

2πr2e−2r/a 1

[−e iQr cos θ

∣∣∣π0dr

∫ ∞0

2πr2e−2r/a 1

[e iQr − e−iQr

∫ ∞0

f 01s(~Q) =

∫e−2r/ae i

f 01s(~Q) =

∫ ∞0

2πr2e−2r/a

∫ π

∫ ∞0

2πr2e−2r/a 1

[−e iQr cos θ

∣∣∣π0dr

∫ ∞0

2πr2e−2r/a 1

[e iQr − e−iQr

∫ ∞0

f 01s(~Q) =

∫e−2r/ae i

f 01s(~Q) =

∫ ∞0

2πr2e−2r/a

∫ π

∫ ∞0

2πr2e−2r/a 1

[−e iQr cos θ

∣∣∣π0dr

∫ ∞0

2πr2e−2r/a 1

[e iQr − e−iQr

∫ ∞0

f 01s(~Q) =

∫e−2r/ae i

f 01s(~Q) =

∫ ∞0

2πr2e−2r/a

∫ π

∫ ∞0

2πr2e−2r/a 1

[−e iQr cos θ

∣∣∣π0dr

∫ ∞0

2πr2e−2r/a 1

[e iQr − e−iQr

∫ ∞0

f 01s(~Q) =

∫e−2r/ae i

f 01s(~Q) =

∫ ∞0

2πr2e−2r/a

∫ π

∫ ∞0

2πr2e−2r/a 1

[−e iQr cos θ

∣∣∣π0dr

∫ ∞0

2πr2e−2r/a 1

[e iQr − e−iQr

∫ ∞0

f 01s(~Q) =

∫e−2r/ae i

f 01s(~Q) =

∫ ∞0

2πr2e−2r/a

∫ π

∫ ∞0

2πr2e−2r/a 1

[−e iQr cos θ

∣∣∣π0dr

∫ ∞0

2πr2e−2r/a 1

[e iQr − e−iQr

∫ ∞0

Form factor calculation

f 01s(~Q) =

∫ ∞0

If we write sin(Qr) = Im[e iQr

]then the integral becomes

f 01s(~Q) =

∫ ∞0

re−2r/aIm[e iQr

[∫ ∞0

re−2r/ae iQrdr

this can be integrated by parts with

u = r dv = e−r(2/a−iQ)dr

du = dr v = −e−r(2/a−iQ)

(2/a− iQ)

f 01s(~Q) =

[re−r(2/a−iQ)

(2/a− iQ)

∣∣∣∣∣∞

∫ ∞0

e−r(2/a−iQ)

(2/a− iQ)dr

f 01s(~Q) =

∫ ∞0

f 01s(~Q) =

∫ ∞0

re−2r/aIm[e iQr

[∫ ∞0

re−2r/ae iQrdr

(2/a− iQ)

f 01s(~Q) =

[re−r(2/a−iQ)

(2/a− iQ)

∣∣∣∣∣∞

∫ ∞0

e−r(2/a−iQ)

(2/a− iQ)dr

f 01s(~Q) =

∫ ∞0

f 01s(~Q) =

∫ ∞0

re−2r/aIm[e iQr

[∫ ∞0

re−2r/ae iQrdr

]this can be integrated by parts with

(2/a− iQ)

f 01s(~Q) =

[re−r(2/a−iQ)

(2/a− iQ)

∣∣∣∣∣∞

∫ ∞0

e−r(2/a−iQ)

(2/a− iQ)dr

f 01s(~Q) =

∫ ∞0

f 01s(~Q) =

∫ ∞0

re−2r/aIm[e iQr

[∫ ∞0

re−2r/ae iQrdr

(2/a− iQ)

f 01s(~Q) =

[re−r(2/a−iQ)

(2/a− iQ)

∣∣∣∣∣∞

∫ ∞0

e−r(2/a−iQ)

(2/a− iQ)dr

f 01s(~Q) =

∫ ∞0

f 01s(~Q) =

∫ ∞0

re−2r/aIm[e iQr

[∫ ∞0

re−2r/ae iQrdr

(2/a− iQ)

f 01s(~Q) =

[re−r(2/a−iQ)

(2/a− iQ)

∣∣∣∣∣∞

∫ ∞0

e−r(2/a−iQ)

(2/a− iQ)dr

f 01s(~Q) =

∫ ∞0

f 01s(~Q) =

∫ ∞0

re−2r/aIm[e iQr

[∫ ∞0

re−2r/ae iQrdr

(2/a− iQ)

f 01s(~Q) =

[re−r(2/a−iQ)

(2/a− iQ)

∣∣∣∣∣∞

∫ ∞0

e−r(2/a−iQ)

(2/a− iQ)dr

f 01s(~Q) =

∫ ∞0

f 01s(~Q) =

∫ ∞0

re−2r/aIm[e iQr

[∫ ∞0

re−2r/ae iQrdr

(2/a− iQ)

f 01s(~Q) =

[re−r(2/a−iQ)

(2/a− iQ)

∣∣∣∣∣∞

∫ ∞0

e−r(2/a−iQ)

(2/a− iQ)dr

]C. Segre (IIT) PHYS 570 - Fall 2015 February 24, 2015 14 / 17

f 01s(~Q) =

[re−r(2/a−iQ)

(2/a− iQ)

∣∣∣∣∣∞

∫ ∞0

e−r(2/a−iQ)

(2/a− iQ)dr

the first term becomes zero because re−r(2/a−iQ) → 0 as r → 0, thesecond is easily integrated

f 01s(~Q) =

[− e−r(2/a−iQ)

(2/a− iQ)2

∣∣∣∣∣∞

(2/a− iQ)2

[(2/a + iQ)2

(2/a− iQ)2(2/a + iQ)2

[(2/a)2 + i(4Q/a)− Q2

[(2/a)2 + Q2]2

f 01s(~Q)

(a/2)4(4Q/a)

[1 + (Qa/2)2]2=

[1 + (Qa/2)2]2

f 01s(~Q) =

[re−r(2/a−iQ)

(2/a− iQ)

∣∣∣∣∣∞

∫ ∞0

e−r(2/a−iQ)

(2/a− iQ)dr

]the first term becomes zero because re−r(2/a−iQ) → 0 as r → 0, thesecond is easily integrated

f 01s(~Q) =

[− e−r(2/a−iQ)

(2/a− iQ)2

∣∣∣∣∣∞

(2/a− iQ)2

[(2/a + iQ)2

(2/a− iQ)2(2/a + iQ)2

[(2/a)2 + i(4Q/a)− Q2

[(2/a)2 + Q2]2

f 01s(~Q)

(a/2)4(4Q/a)

[1 + (Qa/2)2]2=

[1 + (Qa/2)2]2

f 01s(~Q) =

[re−r(2/a−iQ)

(2/a− iQ)

∣∣∣∣∣∞

∫ ∞0

e−r(2/a−iQ)

(2/a− iQ)dr

f 01s(~Q) =

[− e−r(2/a−iQ)

(2/a− iQ)2

∣∣∣∣∣∞

(2/a− iQ)2

[(2/a + iQ)2

(2/a− iQ)2(2/a + iQ)2

[(2/a)2 + i(4Q/a)− Q2

[(2/a)2 + Q2]2

f 01s(~Q)

(a/2)4(4Q/a)

[1 + (Qa/2)2]2=

[1 + (Qa/2)2]2

f 01s(~Q) =

[re−r(2/a−iQ)

(2/a− iQ)

∣∣∣∣∣∞

∫ ∞0

e−r(2/a−iQ)

(2/a− iQ)dr

f 01s(~Q) =

[− e−r(2/a−iQ)

(2/a− iQ)2

∣∣∣∣∣∞

(2/a− iQ)2

[(2/a + iQ)2

(2/a− iQ)2(2/a + iQ)2

[(2/a)2 + i(4Q/a)− Q2

[(2/a)2 + Q2]2

f 01s(~Q)

(a/2)4(4Q/a)

[1 + (Qa/2)2]2=

[1 + (Qa/2)2]2

f 01s(~Q) =

[re−r(2/a−iQ)

(2/a− iQ)

∣∣∣∣∣∞

∫ ∞0

e−r(2/a−iQ)

(2/a− iQ)dr

f 01s(~Q) =

[− e−r(2/a−iQ)

(2/a− iQ)2

∣∣∣∣∣∞

(2/a− iQ)2

[(2/a + iQ)2

(2/a− iQ)2(2/a + iQ)2

[(2/a)2 + i(4Q/a)− Q2

[(2/a)2 + Q2]2

f 01s(~Q)

(a/2)4(4Q/a)

[1 + (Qa/2)2]2=

[1 + (Qa/2)2]2

f 01s(~Q) =

[re−r(2/a−iQ)

(2/a− iQ)

∣∣∣∣∣∞

∫ ∞0

e−r(2/a−iQ)

(2/a− iQ)dr

f 01s(~Q) =

[− e−r(2/a−iQ)

(2/a− iQ)2

∣∣∣∣∣∞

(2/a− iQ)2

[(2/a + iQ)2

(2/a− iQ)2(2/a + iQ)2

[(2/a)2 + i(4Q/a)− Q2

[(2/a)2 + Q2]2

f 01s(~Q)

(a/2)4(4Q/a)

[1 + (Qa/2)2]2=

[1 + (Qa/2)2]2

f 01s(~Q) =

[re−r(2/a−iQ)

(2/a− iQ)

∣∣∣∣∣∞

∫ ∞0

e−r(2/a−iQ)

(2/a− iQ)dr

f 01s(~Q) =

[− e−r(2/a−iQ)

(2/a− iQ)2

∣∣∣∣∣∞

(2/a− iQ)2

[(2/a + iQ)2

(2/a− iQ)2(2/a + iQ)2

[(2/a)2 + i(4Q/a)− Q2

[(2/a)2 + Q2]2

f 01s(~Q)

(a/2)4(4Q/a)

[1 + (Qa/2)2]2

f 01s(~Q) =

[re−r(2/a−iQ)

(2/a− iQ)

∣∣∣∣∣∞

∫ ∞0

e−r(2/a−iQ)

(2/a− iQ)dr

f 01s(~Q) =

[− e−r(2/a−iQ)

(2/a− iQ)2

∣∣∣∣∣∞

(2/a− iQ)2

[(2/a + iQ)2

(2/a− iQ)2(2/a + iQ)2

[(2/a)2 + i(4Q/a)− Q2

[(2/a)2 + Q2]2

]f 01s(~Q) =

(a/2)4(4Q/a)

[1 + (Qa/2)2]2=

[1 + (Qa/2)2]2

1s and atomic form factors

f 01s(~Q) =

[1 + (Qa/2)2]2

This partial form factor will varywith Z due to the Coulomb inter-action

In principle, one can compute thefull atomic form factors, however,it is more useful to tabulate the ex-perimentally measured form factors

f 0 (Q/4π) =4∑

aje−bj sin2 θ/λ2

+ c =4∑

aje−bj (Q/4π)2

f 01s(~Q) =

[1 + (Qa/2)2]2

f 0 (Q/4π) =4∑

+ c =4∑

aje−bj (Q/4π)2

f 01s(~Q) =

[1 + (Qa/2)2]2

0 1 2 3 4 5

f0 1s(Q

f 0 (Q/4π) =4∑

+ c =4∑

aje−bj (Q/4π)2

f 01s(~Q) =

[1 + (Qa/2)2]2

In principle, one can compute thefull atomic form factors, however,it is more useful to tabulate the ex-perimentally measured form factors 0 1 2 3 4 5

f0 1s(Q

f 0 (Q/4π) =4∑

+ c =4∑

aje−bj (Q/4π)2

f 01s(~Q) =

[1 + (Qa/2)2]2

f 0 (Q/4π) =4∑

+ c =4∑

aje−bj (Q/4π)2

Two hydrogen atoms

Previously we derived the scat-tering intensity from two local-ized electrons both fixed andrandomly oriented to the x-rays.

When we now replace the twolocalized electrons with hydro-gen atoms, we have, for fixedatoms.

If we allow the hydrogen atomsto be randomly oriented wehave.

0 0.5 1 1.5 2

Q (units of 2π/r)

nsity (

units o

f r2 o

Two hydrogen atoms

0 0.5 1 1.5 2

Q (units of 2π/r)

nsity (

units o

f r2 o

Two hydrogen atoms

0 0.5 1 1.5 2

Q (units of 2π/r)

nsity (

units o

f r2 o

Two hydrogen atoms

0 0.5 1 1.5 2

Q (units of 2π/r)

nsity (

units o

f r2 o

Two hydrogen atoms

0 0.5 1 1.5 2

Q (units of 2π/r)

nsity (

units o

f r2 o

Today’s Outline - February 24, 2015phys.iit.edu/~segre/phys570/15S/lecture_11.pdfToday’s Outline...

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