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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Why multiphoton exitations advantages disadvantages one color experiments data

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


Why multiphoton exitations advantages disadvantages one color experiments data

Simulation:

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

(0,0)


Why multiphoton exitations advantages disadvantages one color experiments data

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)


Why multiphoton exitations advantages disadvantages one color experiments data

Fig. 2

(2+1) REMPI spectra of I2:

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

(v1,v0)


Why multiphoton exitations advantages disadvantages one color experiments data

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


Why multiphoton exitations advantages disadvantages one color experiments data

AB+ + e

:

AB**

|i4>

|i3>

Properties of AB* and AB:

- energy configurations

- molecular geometries

|i2>

|i1>

AB

i.e.:


Why multiphoton exitations advantages disadvantages one color experiments data

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


Why multiphoton exitations advantages disadvantages one color experiments data

HBr:

16


Why multiphoton exitations advantages disadvantages one color experiments data

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


Why multiphoton exitations advantages disadvantages one color experiments data

DJ = ±1,.. ,±n; n = odd; DW = 0

DJ = 0 ,±2,.. ,±n; n = even DW = 0

HBr:

16


Why multiphoton exitations advantages disadvantages one color experiments data

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


Why multiphoton exitations advantages disadvantages one color experiments data

18

B´= 8.39±0.05 cm-1

D´= (0.85±0.10)x10-3cm-1

n0 = 82837±3 cm-1


Why multiphoton exitations advantages disadvantages one color experiments data

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 = ?????)


Why multiphoton exitations advantages disadvantages one color experiments data

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


Why multiphoton exitations advantages disadvantages one color experiments data

Complicated spectra, analyses / Example I:

HCl, (3+1) REMPI:

n

cm-1

3 x (1/l=333 nm)


Why multiphoton exitations advantages disadvantages one color experiments data

n

cm-1

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

HCl, (3+1) REMPI / Simulation:

???!!

???!!

???!!

OK

OK


Why multiphoton exitations advantages disadvantages one color experiments data

“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


Why multiphoton exitations advantages disadvantages one color experiments data

Difference spectra(2) = “exp. – diff. spectra(1)” / Simulation:


Why multiphoton exitations advantages disadvantages one color experiments data

“Difference spectra “(1) / Simulation:


Why multiphoton exitations advantages disadvantages one color experiments data

Complicated spectra, analyses / Example II:

(2,0) -band


Why multiphoton exitations advantages disadvantages one color experiments data

NO

z

z

W= 3/2

W= 1/2

1

z

Spin-rot.

interaction

D 2S:

Orbit-rot.

interaction

X 2P:

Spin-orbit

interaction


Why multiphoton exitations advantages disadvantages one color experiments data

(1,1)

(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´´


Why multiphoton exitations advantages disadvantages one color experiments data

2S

(11)

(22)

(12)

(21)

2P

, T=298K

(2,0)


Why multiphoton exitations advantages disadvantages one color experiments data

(2,0)


Why multiphoton exitations advantages disadvantages one color experiments data

(2,0)


Why multiphoton exitations advantages disadvantages one color experiments data

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


Why multiphoton exitations advantages disadvantages one color experiments data

AB#/A#+B#

State interactions/

AB** <->AB#

&

dissociation processes

AB** -> A# + B#

?

AB+ + e

AB**

:

|i4>

|i3>

|i2>

|i1>

AB


Why multiphoton exitations advantages disadvantages one color experiments data

HCl; (3+1)REMPI

j3S0- <- X1S+

(0,0)

?


Why multiphoton exitations advantages disadvantages one color experiments data

j3S0- <- X1S+

(0,0)

(3+1)REMPI

?

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

?


Why multiphoton exitations advantages disadvantages one color experiments data

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

explanation:

8

7

v´=24

(3+1)REMPI


Why multiphoton exitations advantages disadvantages one color experiments data

Rotational perturbation

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)


Why multiphoton exitations advantages disadvantages one color experiments data

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


Why multiphoton exitations advantages disadvantages one color experiments data

AB+ + e

:

AB**

|i4>

|i3>

|i2>

Mechanism of nxhn absorption /

ionization; involvement of

intermediate states.

?

|i1>

AB


Why multiphoton exitations advantages disadvantages one color experiments data

N,T: I 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


Why multiphoton exitations advantages disadvantages one color experiments data

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

21

m12 /m32 = 0.90±0.15


Why multiphoton exitations advantages disadvantages one color experiments data

W´=1

(P)

W´=0

(S)

W´=0

(S)

Four

paths:

W´´=0(S)

W´´=0(S)

22


Why multiphoton exitations advantages disadvantages one color experiments data

Major path

for HCl:

E(1S+)

X(1S+):

Paths vs m12 and m32 :

23

-vs exp.: m12 /m32 = 0.90±0.15


Why multiphoton exitations advantages disadvantages one color experiments data

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


Why multiphoton exitations advantages disadvantages one color experiments data

HBr

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

Na


Why multiphoton exitations advantages disadvantages one color experiments data

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

Na

effect?

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


Why multiphoton exitations advantages disadvantages one color experiments data

detect / measure HBr by REMPI: observe kinetic energy.

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

Na

effect?

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


Why multiphoton exitations advantages disadvantages one color experiments data

IREMPI

n


Why multiphoton exitations advantages disadvantages one color experiments data

2 x (1/l=255nm)

3 x (1/l=382nm)

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


Why multiphoton exitations advantages disadvantages one color experiments data

i.e.:

»straight line

25oC

(3+1)REMPI spectra

and s

useful to determine

N(J)

Line fit

Besta

beina lína


Why multiphoton exitations advantages disadvantages one color experiments data

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


Why multiphoton exitations advantages disadvantages one color experiments data

3dpF1Su+ <-<-<- X1Sg +

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


Why multiphoton exitations advantages disadvantages one color experiments data

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


Why multiphoton exitations advantages disadvantages one color experiments data

AB = CdAr:

(v1,v0)

|1>

A30+<- X10+

v1+1

v1

v1-1

Energy

v0

|0>

r (A-B)


Why multiphoton exitations advantages disadvantages one color experiments data

(v1,v0)

AB = I2:

|1>

v1+1

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

v1

v1-1

Energy

v0

|0>

r (A-B)


Why multiphoton exitations advantages disadvantages one color experiments data

AB nxhn– (|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)


Why multiphoton exitations advantages disadvantages one color experiments data

V0=0

V1= 0 1 2 3 4 5


Why multiphoton exitations advantages disadvantages one color experiments data

V0=0

V1= 0 1 2 3 4 5


Why multiphoton exitations advantages disadvantages one color experiments data

V0=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


Why multiphoton exitations advantages disadvantages one color experiments data

Example: Two-colour optical doule resonance (ODR)

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


Why multiphoton exitations advantages disadvantages one color experiments data

I2+ + e

Energy

[I+I-]* 0 g

I2* B 3P0 u

I2 X 1S+ g

r(I-I)


Why multiphoton exitations advantages disadvantages one color experiments data

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


Why multiphoton exitations advantages disadvantages one color experiments data

Acknowledgments:

Iceland:

:Benedikt G. Waage, MS student

Jón Matthíasson,

Oddur Ingólfsson, PhD

Kristján Matthíasson, MS student

Victor Huasheng Wang, research scientist

Ágúst Kvaran, professor

24


Why multiphoton exitations advantages disadvantages one color experiments data

Acknowledgments:

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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