II. Multi- photon excitation / ionization processes
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II. Multi- photon excitation / ionization processes. Why multiphoton exitations(?); advantages/disadvantages One color experiments / data Experimental methods: Multiphoton ionization (MPI & REMPI) Data interpretations / theory: “What to see and what not to see(?)” Results / examples:

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II. Multi- photon excitation / ionization processes

  • Why multiphoton exitations(?); advantages/disadvantages

  • One color experiments / data

    • Experimental methods: Multiphoton ionization (MPI & REMPI)

    • Data interpretations / theory: “What to see and what not to see(?)”

    • Results / examples:

  • - characterization of state properties / energies

  • - (2+1) vs (3+1) REMPI

  • - ”New” states observed

  • - analysis of complicated spectra

  • - state interactions

  • - multi-photon absorption “mechanism”

  • - energy distribution in molecules

  • - polyatomic molecules

  • Two color experiments / data


Simulation:

i(3D2) <- X(1S+)

(0,0)


Simulation:

Be´/ Bf´ = 7.975/7.969 ±0.030cm-1

De´/Df´= (0.55/0.50 ± 0.10)x10-3 cm-1

n0 = 78625 ± 2 cm-1

E´(J) = B´J(J+1) – D´J2(J+1)2

n0 = E´(v´=0) – E´´(v´´=0)

for

i(3D2) <- X(1S+)

(0,0)


Fig. 2

(2+1) REMPI spectra of I2:

I2; [2P1/2]c6s;1g <-<- X 0g

(v1,v0)


DOP

Fig. 3

I2; [2P1/2]c6s;1g <-<- X 0g

(2+1) REMPI spectra of I2:

as well as

Rotational line series:

O: J-2 <- J; P: J-1 <- J

Q: J <- J

R: J+1 <- J; S: J+2 <- J

Exp.

Calc.

(v1,v0) =

Dn / cm-1


AB+ + e

:

AB**

|i4>

|i3>

Properties of AB* and AB:

- energy configurations

- molecular geometries

|i2>

|i1>

AB

i.e.:


II. Multi- photon excitation / ionization processes

  • Why multiphoton exitations(?); advantages/disadvantages

  • One color experiments / data

    • Experimental methods: Multiphoton ionization (MPI & REMPI)

    • Data interpretations / theory: “What to see and what not to see(?)”

    • Results / examples:

  • - characterization of state properties / energies

  • - (2+1) vs (3+1) REMPI

  • - ”New” states observed

  • - analysis of complicated spectra

  • - state interactions

  • - multi-photon absorption “mechanism”

  • - energy distribution in molecules

  • - polyatomic molecules

  • Two color experiments / data


HBr:

16


Total angular

momentum changes

For W´=0 W ´´=0:

J-3;N

J-2;O

J-1;P

J:Q

J+1;R

J+2;S

J+3;T

DJ = ±1

DJ = ±1

DJ = ±1

J

z

= 0


DJ = ±1,.. ,±n; n = odd; DW = 0

DJ = 0 ,±2,.. ,±n; n = even DW = 0

HBr:

16


II. Multi- photon excitation / ionization processes

  • Why multiphoton exitations(?); advantages/disadvantages

  • One color experiments / data

    • Experimental methods: Multiphoton ionization (MPI & REMPI)

    • Data interpretations / theory: “What to see and what not to see(?)”

    • Results / examples:

  • - characterization of state properties / energies

  • - (2+1) vs (3+1) REMPI

  • - ”New” states observed

  • - analysis of complicated spectra

  • - state interactions

  • - multi-photon absorption “mechanism”

  • - energy distribution in molecules

  • - polyatomic molecules

  • Two color experiments / data


18

B´= 8.39±0.05 cm-1

D´= (0.85±0.10)x10-3cm-1

n0 = 82837±3 cm-1


W´=3(F)

W´=2(D)

W´=1(P)

W´=0(S)

2xhn

3xhn

3xhn

½i >

1xhn

2xhn

3xhn

“New” state: L1F3 (n0 = 82837±3 cm-1)

W´´=0(S)

“New” state, not detected before:

19

Predicted state ((s2p3)5dd)

in this region: L1F3 (n0 = ?????)


II. Multi- photon excitation / ionization processes

  • Why multiphoton exitations(?); advantages/disadvantages

  • One color experiments / data

    • Experimental methods: Multiphoton ionization (MPI & REMPI)

    • Data interpretations / theory: “What to see and what not to see(?)”

    • Results / examples:

  • - characterization of state properties / energies

  • - (2+1) vs (3+1) REMPI

  • - ”New” states observed

  • - analysis of complicated spectra

  • - state interactions

  • - multi-photon absorption “mechanism”

  • - energy distribution in molecules

  • - polyatomic molecules

  • Two color experiments / data


Complicated spectra, analyses / Example I:

HCl, (3+1) REMPI:

n

cm-1

3 x (1/l=333 nm)


n

cm-1

Find “difference spectra” / “exp. – Calc.”

HCl, (3+1) REMPI / Simulation:

???!!

???!!

???!!

OK

OK


“Difference spectra(1)” / “exp. – Calc.”:

exp.

-

calc.

3 x (1/l=333 nm)

HCl, (3+1)

REMPI

exp. – calc./

“Diff.sp.(1)”

n

cm-1





NO Simulation:

z

z

W= 3/2

W= 1/2

1

z

Spin-rot.

interaction

D 2S:

Orbit-rot.

interaction

X 2P:

Spin-orbit

interaction


(1,1) Simulation:

(1,2)

(2,1)

(2,2)

E1´

E2´

2S

Spin-rot.

interaction

Cv´

2P3/2

Orbit-rot.

interaction

2P1/2

Av´´=0

Cv´´=0

E1´´

E2´´


2 Simulation:S

(11)

(22)

(12)

(21)

2P

, T=298K

(2,0)


(2,0) Simulation:


(2,0) Simulation:


II. Multi- photon excitation / ionization processes Simulation:

  • Why multiphoton exitations(?); advantages/disadvantages

  • One color experiments / data

    • Experimental methods: Multiphoton ionization (MPI & REMPI)

    • Data interpretations / theory: “What to see and what not to see(?)”

    • Results / examples:

  • - characterization of state properties / energies

  • - (2+1) vs (3+1) REMPI

  • - ”New” states observed

  • - analysis of complicated spectra

  • - state interactions

  • - multi-photon absorption “mechanism”

  • - energy distribution in molecules

  • - polyatomic molecules

  • Two color experiments / data


AB Simulation:#/A#+B#

State interactions/

AB** <->AB#

&

dissociation processes

AB** -> A# + B#

?

AB+ + e

AB**

:

|i4>

|i3>

|i2>

|i1>

AB


HCl; (3+1)REMPI Simulation:

j3S0- <- X1S+

(0,0)

?


j Simulation:3S0- <- X1S+

(0,0)

(3+1)REMPI

?

Comparison of (2+1) og (3+1)REMPI:

?


State interaction / perturbation j <->V( Simulation:1S+) / interaction strength

explanation:

8

7

v´=24

(3+1)REMPI


Rotational perturbation Simulation:

observed in vibrational

band due to the transition

I2; [2P3/2]c5s;1g <-<- X 0g,

v1 = 0, v0 = 1

::

Because of state interactions:

[2P3/2]c5s;1g <-> D´(2g)


II. Multi- photon excitation / ionization processes Simulation:

  • Why multiphoton exitations(?); advantages/disadvantages

  • One color experiments / data

    • Experimental methods: Multiphoton ionization (MPI & REMPI)

    • Data interpretations / theory: “What to see and what not to see(?)”

    • Results / examples:

  • - characterization of state properties / energies

  • - (2+1) vs (3+1) REMPI

  • - ”New” states observed

  • - analysis of complicated spectra

  • - state interactions

  • - multi-photon absorption “mechanism”

  • - energy distribution in molecules

  • - polyatomic molecules

  • Two color experiments / data


AB Simulation:+ + e

:

AB**

|i4>

|i3>

|i2>

Mechanism of nxhn absorption /

ionization; involvement of

intermediate states.

?

|i1>

AB


N,T: I Simulation:µm32s3

P,R: I µm12s1 + m32s3

I(N,T) / I(P,R) depend on

m12 and m32 or m12 /m32

Adjust m12 and m32

to obtain best fit:

W´´=0(S)

W´=0(S) W´´=0(S)

20

I µm12s1 + m32s3


HCl, E( Simulation:1S+) X(1S+), (3+1)REMPI

21

m12 /m32 = 0.90±0.15


W Simulation:´=1

(P)

W´=0

(S)

W´=0

(S)

Four

paths:

W´´=0(S)

W´´=0(S)

22


Major path Simulation:

for HCl:

E(1S+)

X(1S+):

Paths vs m12 and m32 :

23

-vs exp.: m12 /m32 = 0.90±0.15


II. Multi- photon excitation / ionization processes Simulation:

  • Why multiphoton exitations(?); advantages/disadvantages

  • One color experiments / data

    • Experimental methods: Multiphoton ionization (MPI & REMPI)

    • Data interpretations / theory: “What to see and what not to see(?)”

    • Results / examples:

  • - characterization of state properties / energies

  • - (2+1) vs (3+1) REMPI

  • - ”New” states observed

  • - analysis of complicated spectra

  • - state interactions

  • - multi-photon absorption “mechanism”

  • - energy distribution in molecules

  • - polyatomic molecules

  • Two color experiments / data


H Simulation:Br

Surface science studies/ collaboration work with J.C. Polanyi, Toronto:

Na


Surface science studies/ collaboration work with J.C. Polanyi, Toronto:

Na

effect?

i.e.: 1) hn + NaBrH(s) -> NaBr(s) + H(g)


detect / measure HBr by REMPI: observe kinetic energy. Polanyi, Toronto:

Surface science studies/ collaboration work with J.C. Polanyi, Toronto:

Na

effect?

i.e.: 2) hn + NaBrH(s) -> Na(s) + HBr#(g)


I Polanyi, Toronto:REMPI

n


2 x (1/ Polanyi, Toronto:l=255nm)

3 x (1/l=382nm)

(3+1)REMPI simpler spectrum / “more convenient” wavelength


i.e.: Polanyi, Toronto:

»straight line

25oC

(3+1)REMPI spectra

and s

useful to determine

N(J)

Line fit

Besta

beina lína


II. Multi- photon excitation / ionization processes Polanyi, Toronto:

  • Why multiphoton exitations(?); advantages/disadvantages

  • One color experiments / data

    • Experimental methods: Multiphoton ionization (MPI & REMPI)

    • Data interpretations / theory: “What to see and what not to see(?)”

    • Results / examples:

  • - characterization of state properties / energies

  • - (2+1) vs (3+1) REMPI

  • - ”New” states observed

  • - analysis of complicated spectra

  • - state interactions

  • - multi-photon absorption “mechanism”

  • - energy distribution in molecules

  • - polyatomic molecules

  • Two color experiments / data


3d Polanyi, Toronto:pF1Su+ <-<-<- X1Sg +

V. Blanchet et al., J. Chem. Phys., 119(7), 3751, (2003):


II. Multi- photon excitation / ionization processes Polanyi, Toronto:

  • Why multiphoton exitations(?); advantages/disadvantages

  • One color experiments / data

    • Experimental methods: Multiphoton ionization (MPI & REMPI)

    • Data interpretations / theory: “What to see and what not to see(?)”

    • Results / examples:

  • - characterization of state properties / energies

  • - (2+1) vs (3+1) REMPI

  • - ”New” states observed

  • - analysis of complicated spectra

  • - state interactions

  • - multi-photon absorption “mechanism”

  • - energy distribution in molecules

  • - polyatomic molecules

  • Two color experiments / data


A Polanyi, Toronto:B = CdAr:

(v1,v0)

|1>

A30+<- X10+

v1+1

v1

v1-1

Energy

v0

|0>

r (A-B)


(v Polanyi, Toronto:1,v0)

AB = I2:

|1>

v1+1

[2P1/2]c6s;1g <-<- X 0g

v1

v1-1

Energy

v0

|0>

r (A-B)


AB nxh Polanyi, Toronto:n– (|1>, |0> )/(v1+i,v0)

excitations:

(v1+1)

I

v1 +1

s

v1

|1>

(v1-1)

Exp.

v1 -1

(v1)

DE10

nxhn

v0

|0>

Calc.

n

:

:

:

DE-10

DE00

DE+10

B-O approximation, etc.

i.e.:

nhn + AB -> AB*

mhn + AB -> AB+ + e- (Ekin = 0)


V Polanyi, Toronto:0=0

V1= 0 1 2 3 4 5


V Polanyi, Toronto:0=0

V1= 0 1 2 3 4 5


V Polanyi, Toronto:0=0

V1= 0 1 2 3 4 5

  • Hence: excited states with large(r) internuclear distances can

  • not easily be accessed in “simultaneous” excitation

  • Use double resonance technique


Example: Two-colour optical doule resonance (ODR) Polanyi, Toronto:

ionization of I2:

I2+ + e

Energy

[I+I-]* 0 g

(1+1)REMPI

1´ excitation

I2* B 3P0 u

((1´+1)+1) REMPI

r(I-I)

I2 X 1S+ g


I Polanyi, Toronto:2+ + e

Energy

[I+I-]* 0 g

I2* B 3P0 u

I2 X 1S+ g

r(I-I)


Please visit: Polanyi, Toronto:http://www.raunvis.hi.is/~agust/


Acknowledgments: Polanyi, Toronto:

Iceland:

:Benedikt G. Waage, MS student

Jón Matthíasson,

Oddur Ingólfsson, PhD

Kristján Matthíasson, MS student

Victor Huasheng Wang, research scientist

Ágúst Kvaran, professor

24


Acknowledgments: Polanyi, Toronto:

24

Collaborators:

:Robert J. Donovan, Prof., Edinburgh University, UK

Timothy G. Wright, University of Sussex, UK

Lars Madsen, Aarhus, Denmark

NORFA network participants (?)

  • Funds:

  • Icelandic Science foundation

  • University Research Fund

  • NORFA / NORDPLUS


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