Download pdf - Muon Spectroscopy of Molecules · 2017. 5. 15. · Agrees with NMR & QENS values. Photoelectron spectroscopic evidence to show the drop in energy of the d-orbitals across the Periodic

MuonMuon Spectroscopy of MoleculesSpectroscopy of Molecules

Upali Upali A. A. JayasooriyaJayasooriya

School of Chemical Sciences and PharmacySchool of Chemical Sciences and Pharmacy

University of East University of East AngliaAnglia

NorwichNorwich

UKUK

IntroductionIntroduction

• Muon Muon states in matterstates in matter

Implanted positiveImplanted positive muonsmuons may exist in any of the may exist in any of the following forms.following forms.

a) a) MuonMuon µµ++

b) b) MuoniumMuonium µµ++ee--

c) Part of a radicalc) Part of a radical

µµSRSR•• Properties of Properties of MuonsMuons??

Mass = 0.11 protonMass = 0.11 proton

Charge = +eCharge = +e

Spin = 1/2Spin = 1/2

Magnetic moment = 3.18 x protonMagnetic moment = 3.18 x proton

µµSRSR

•• Properties of Properties of MuoniumMuonium [[µµ++ee--]]

Isotope Mass/me Reduced mass/me Bohr radius/nm Ionisation energy/eV

Tritium (3H) 5498 0.9998 0.05290 13.603

Deuterium (2H) 3675 0.9997 0.05293 13.602

Protium (1H) 1847 0.9995 0.05292 13.599

Muonium (Mu) 208 0.9952 0.05315 13.541

µµSRSR

•• Molecules with Molecules with MuoniumMuonium [[µµ++ee--]]

Some of the names to look out for

•Paul Percival•Emil Roduner•David Walker•Donald G. Fleming•Christopher Rhodes•Brian Webster•Rod Macrae

µµSRSR

•• Molecules with Molecules with MuoniumMuonium [[µµ++ee--]]Chemiluminescence from the

exiplex molecule NeMu*

S. Baer et. al. J. Chem. Phys. 101 (1994) 1202

Dissociative state, Ne + Mu

Exciplex, NeMu*

Ne-Mu distance

Molecular potential energy

Prompt

Delayed

Muon - Electron system; Breit - Rabi diagram

Singlet

Energy

Magnetic FieldTriplet

Aµ

e- µ+

⌧3>

⌧2>

⌧4>

⌧1>

ms

+1

0

-10

Pashen-Back regime

H = hAµ S.I + hωeSz + hωµIz

Muon - Electron system; Breit - Rabi diagram

Singlet

Energy

Magnetic Field

Triplet

Aµ ν24

ν12

ν34

e- µ+

+ +

+ -

- -

- +

⌧3>

⌧2>

⌧4>

⌧1>

ms

+1

0

-1

0

Polarisation

Relaxation

LF

-time differential

Rotation

TF

ALC

LF

-time integral

µµSRSR


carbonyl groups:carbonyl groups: C = OC = OEn

ergy

σ

nπ

σ∗

π∗ LUMO

Mu

TF-MuSR spectra of

(a) 4-Fluoroacetophenone,

(b) 4-Chloroacetophenone

& (c) 4-Methylacetophenone

at 200 mT and 300 K

µµSRSR


Mu.

Mu.

EtheneCH2 = CH2

DNA

µµSRSR


4

5N7

N9 N3

2

N16

8

NH26

R

4

5N7

N9 N3

2

NH16

8

R

O

NH22

6

5

N1

2

NH34

O4

O2

R

CH3

6

5

N1

2

NH34

O4

O2

R

URACIL THYMINE CYTOSINE

GUANINE ADENINE

6

5

N 1

2

N34

NH24

O2

R

µµSRSR•• Molecules with Molecules with MuoniumMuonium [[µµ++ee--]]

1.4 1.6 1.8 2.0 2.2 2.4 2.6

-0.4

-0.3

-0.2

-0.1

0.0

0.1

0.2

0.3

0.4

Field / T

Derivative of polarisation

300K

Adenine

100K

1.3 1.4 1.5 1.6 1.7 1.8 1.9 2.0 2.1 2.2

1.4

1.6

1.8

2.0

2.2

2.4 Guanine; C5

Cytosine; C6

Adenine; C2

Uracil; C6

Thymine; C5

Adenine; C8

Guanine; C8

Experimental field / T

Theoretical field / T

ALC |∆M| = 1 resonance features


1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0 3.2

1.4

1.6

1.8

2.0

2.2

2.4

Cytosine; C6α

Uracil; C6α

Cytosine; C5α

Adenine; C8γ

Thymine; OCH

3

Cytosine; C6β Uracil; O

2β

Uracil; C6β



ALC |∆M| = 0 resonance features

0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5

1.0

1.1

1.2

1.3

1.4

1.5

1.6

1.7

1.8

Uracil; O2

Thymine; O2

Uracil; O4



ALC |∆M| = 1 O-Mu adduct resonance features

1 2 3 4

-0.15

-0.10

-0.05

0.00

0.05

0.10

300K

Field / T

Derivative of polarisation

200K

20K

The ALC-µSR spectra ofdsDNA (Herring testes).

The resonance signals observed and assigned for the different bases are indicated as a stick diagram for comparison.

The predicted positions, using the DFT results and the linear correlations, of the other possible addition sites on the bases for which no experimental ALC signals were observed are indicated as dark squares.


Two main types of measurement:

(a) Active observer of a process

Radical formation modifies the process

(b) Passive observer of a process

Measured properties similar to close-shell compound


O

Diallylether

Mu

O

Mu•

O

Mu

•

Rates of Radical Cyclization

P. Burkhatd et. Al. J. Phys. Chem. 88 (1984) 773

k


TF-MuSR


k (338K) = 9.3 x 106 s-1

and compares well with the literature estimates of

k (338K) = 8.8 x 106 s-1

µµSRSR

•• Muon Muon Spin RelaxationSpin Relaxation

sampleµ+

detectors

FB

Measure (F - B)/(F + B) vs Time

Molecular Dynamics

Theory

( )222

22

ωτ1

τ.

x1

x.A2π2.λ

++= δ

( )ijij

2

ijij ω.φ.PMλ =

Coupling of perturbation

Change in muon polarisation

Spectral density of perturbation

S.F.J. Cox and D.S. Sivia, Hyperfine Interactions 87 (1994) 971

H

MuFe

Mu

Fe

H

Mu

Fe

FERROCENE

Fe-Mu radical cp-Mu exo-radical

cp-Mu endo-radical

1 10 100-0.5

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

Field / mT

Relaxation /

µs-1

Ferrocene 300K

0 50 100 150 200 250 300 350 400 450

-0.5

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

Relaxation /

µs-1

Temperature / K

0 50 100 150 200 250 300 350 400-0.05

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

Relaxation /

µs-1

Temperature / K

ï

ï4 ï6 ï8

ï22

ï23

ï24

ï25

ï26

ï

ï

ïln(/

τ ï)ï(1000 / T) / K

ï-1

ï4 ï6 ï8 ï10 ï12 ï14ï22.0

ï22.5

ï23.0

ï23.5

ï24.0

ï24.5

ï25.0

ï25.5

ï26.0

ï

ï

ïln(1/τ ï)

ï(1000 / T) / Kï-1

∆E = 3.4(0.4) kJ mol-1

∆E = 5.8(0.4) kJ mol-1

Α = 6.3(1.7)x1011 s-1

Α = 1.1(0.4)x1012 s-1

Cp

-Mu

re

po

lari

ses

lik

e b

en

zen

eFe

-Mu

e2u

e1g (xz,yz)

e2u

e1g

e1u

a1

a1 a1g

a1u

d(a1g,e1g,e2g)

e1g

e1u

e2g (x2-y2,xy)

a1g (z2)

e2u

e1g (xz,yz)

e2u

e1g

e1u

a1u

a1g a1g

a1u

d(a1g,e1g,e2g)

e1g

e1u

e2g (x2-y2,xy)

a1g (z2)

∆E = 5.8(0.4) kJ mol-1

Α = 1.1x1012(0.4) s-1

∆E = 3.4(0.4) kJ mol-1

Α = 6.3x1011(1.7) s-1

Agrees with NMR & QENS valuesfor cyclopentadienyl ring rotation

LUMO

LUMO

NON BONDING

ANTI BONDING

I II IIIb IVb Vb VIb VIIb VIIIb Ib IIb III IV V VI VII 0

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 H He

Li Be B C N O F Ne Na Mg Al Si P S Cl Ar K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe Cs Ba La* Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn Fr Ra Ac** Rf Db Sg Bh Hs Mt Uun Uuu Uub Uuq Uuh Uuo

Lanthanides * Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Actinides ** Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr

Benzene chromium tricarbonyl

Cyclopentadienyl manganese tricarbonyl

Ferrocene

Ruthenocene

Osmocene

LUMO non-bonding

LUMO anti-bonding

Agree with NMR and QENS

Do not agree with NMR and QENS

Both types

e2u

e1g (xz,yz)

e2u

e1g

e1u

a1

a1 a1g

a1u

d(a1g,e1g,e2g)

e1g

e1u

e2g (x2-y2,xy)

a1g (z2)

e2u

e1g (xz,yz)

e2u

e1g

e1u

a1u

a1g a1g

a1u

d(a1g,e1g,e2g)

e1g

e1u

e2g (x2-y2,xy)

a1g (z2)

∆E = 5.8(0.4) kJ mol-1

Α = 1.1(0.4) s-1

∆E = 3.4(0.4) kJ mol-1

Α = 6.3(1.7) s-1

Agrees with NMR & QENS values

Photoelectron spectroscopic evidence to show the drop in energy of the d-orbitals across the Periodic Table.

AcknowledgementsAcknowledgements

Julea Butt UEAVasily Oganesyan UEARoger Grinter UEA

Muon Group Members ISIS-RAL & PSI

John Stride UEAGina Aston UEAPenny Hubbard UEALaure Camus UEA

EPSRC for funding