Muon Spectroscopy of Molecules 2017. 5. 15.¢  Agrees with NMR & QENS values. Photoelectron spectroscopic

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  • 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

    M ol ec ul ar  p ot en ti al  e ne rg y

    Prompt

    Delayed

  • Muon - Electron system; Breit - Rabi diagram

    Singlet

    Energy

    Magnetic Field Triplet

    e- µ+

    ⌧3>

    ⌧2>

    ⌧4>

    ⌧1>

    ms

    +1

    0

    -1 0

    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

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

    carbonyl groups:carbonyl groups: C = OC = O En

    er gy

    σ

    n π

    σ∗

    π∗ LUMO

    Mu

  • TF-MuSR spectra of

    (a) 4-Fluoroacetophenone,

    (b) 4-Chloroacetophenone

    & (c) 4-Methylacetophenone

    at 200 mT and 300 K

  • µµSRSR

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

    Mu .

    Mu.

    Ethene CH2 = CH2

  • DNA

  • µµSRSR

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

    4

    5N 7

    N9 N 3

    2

    N 16

    8

    NH2 6

    R

    4

    5N 7

    N9 N 3

    2

    NH 16

    8

    R

    O

    NH22

    6

    5

    N1 2

    NH 34

    O 4

    O2

    R

    CH3

    6

    5

    N1 2

    NH 34

    O 4

    O2

    R

    URACIL  THYMINE  CYTOSINE 

    GUANINE ADENINE 

    6

    5

    N 1 2

    N 34

    NH2 4

    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

    D er iv at iv e  o f  p o la ri sa ti o n

    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; C 5

    Cytosine; C 6

    Adenine; C 2

    Uracil; C 6

    Thymine; C 5

    Adenine; C 8

    Guanine; C 8

     

     

    E x p e ri m e n ta l f ie ld  /  T

    Theoretical field / T

    ALC |∆M| = 1 resonance features 

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

    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; C 6 α

    Uracil; C 6 α

    Cytosine; C 5 α

    Adenine; C 8 γ

    Thymine; O CH

    3

    Cytosine; C 6 β Uracil; O2β

    Uracil; C 6 β

    E xp e ri m e n ta l  fi e ld  /  T

    Theoretical field / T

    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; O 2

    Thymine; O 2

    Uracil; O 4

     

     

    E xp er im en ta l f ie ld  /  T

    Theoretical field / T

    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

    D er iv at iv e  o f  p o la ri sa ti o n

    200K

    20K

    The ALC-µSR spectra of dsDNA (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.

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

    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

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

    O

    Diallylether

    Mu

    O

    Mu•

    O

    Mu

    Rates of Radical Cyclization

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

    k

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

    TF-MuSR

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

    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

    sample µ+

    detectors

    FB

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

  • Molecular Dynamics

    Theory

    ( ) 222

    2 2

    ωτ1 τ

    . x1

    x .A2π2.λ

    ++ = δ

    ( )ijij2ijij 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

    R el ax at io n  / 

    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

     

     

    R e la xa ti o n  / 

    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

     

     

    R e la xa ti o n  / 

    µs -1

    Temperature / K

    ï

    ï4 ï6 ï8

    ï22

    ï23

    ï24

    ï25

    ï26

    ï

    ï

    ïl n (/

    τ ï) ï(1000 / T) / K

    ï-1

    ï4 ï6 ï8 ï10 ï12 ï14 ï22.0

    ï22.5

    ï23.0

    ï23.5

    ï24.0

    ï24.5

    ï25.0

    ï25.5

    ï26.0

    ï

    ï

    ïl n (1 /τ ï)

    ï(1000 / T) / K ï-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-1C p

    -M u

    r e

    p o

    la ri

    se s

    li k

    e b

    e n

    ze n

    e F e

    -M u

  •  

    e2u 

    e1g (xz,yz) 

    e2u

    e1g 

    e1u 

    a1

    a1 a1g 

    a1