1. 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

2. Simulation:
i(3D2) <- X(1S+)
(0,0)

3. for Simulation: i(3D2) <- X(1S+) (0,0)
Be´/ Bf´ = 7.975/7.969 ±0.030 cm-1
De´/Df´= (0.55/0.50 ± 0.10)x10-3 cm-1
n0 = ± 2 cm-1
E´(J) = B´J(J+1) – D´J2(J+1)2
n0 = E´(v´=0) – E´´(v´´=0)
for

4. (2+1) REMPI spectra of I2:
Fig. 2
I2; [2P1/2]c6s;1g <-<- X 0g
(v1,v0)

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

6. i.e.: AB AB+ + e AB** |i1> |i4> |i3> |i2> :
Properties of AB* and AB:
- energy configurations
- molecular geometries

7. 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

8. 16
HBr:

9. Total angular
momentum changes
For W´=0 W ´´=0:
J:Q
J-1;P
J+1;R
J-3;N
J-2;O
J+2;S
J+3;T J
DJ = ±1 z
= 0

10. HBr: DJ = ±1,.. ,±n; n = odd; DW = 016
HBr:
DJ = ±1,.. ,±n; n = odd; DW = 0
DJ = 0 ,±2,.. ,±n; n = even DW = 0

11. 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

12. 18
B´= 8.39±0.05 cm-1
D´= (0.85±0.10)x10-3cm-1
n0 = 82837±3 cm-1

13. “New” state, not detected before:19
W´=3(F)
W´=2(D)
W´=1(P)
W´=0(S)
W´´=0(S)
3xhn
2xhn
3xhn
1xhn
2xhn
3xhn
½i >
Predicted state ((s2p3)5dd)
in this region: L1F3 (n0 = ?????)
“New” state: L1F3 (n0 = 82837±3 cm-1)

14. 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

15. Complicated spectra, analyses / Example I:
HCl, (3+1) REMPI: n
cm-1
3 x (1/l=333 nm)

16. HCl, (3+1) REMPI / Simulation:
cm-1
???!!
???!!
???!! OK OK
Find “difference spectra” / “exp. – Calc.”

17. - “Difference spectra(1)” / “exp. – Calc.”: HCl, (3+1) REMPI n cm-1
3 x (1/l=333 nm) n
cm-1
exp. – calc./
“Diff.sp.(1)”

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

19. “Difference spectra “(1) / Simulation:

20. Complicated spectra, analyses / Example II:
(2,0) -band

21. NO D 2S: X 2P: z z Spin-rot. interaction z W= 3/2 W= 1/2 Orbit-rot.
Spin-orbit
interaction

22. E1´
E2´
(1,1)
(2,2) 2S
Spin-rot.
interaction
(2,1)
(1,2)
Cv´
2P3/2
Orbit-rot.
interaction
2P1/2
Av´´=0
Cv´´=0
E1´´
E2´´

23. , T=298K
(2,0)
(11)
(22)
(21)
(12) 2S 2P

24. (2,0)

25. (2,0)

26. 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

27. AB+ + e
AB** :
State interactions/
AB** <->AB#
&
dissociation processes
AB** -> A# + B# ?
AB#/A#+B#
|i4>
|i3>
|i2>
|i1> AB

28. HCl; (3+1)REMPI
j3S0- <- X1S+
(0,0) ?

29. ? ? Comparison of (2+1) og (3+1)REMPI: j3S0- <- X1S+ (0,0)

30. explanation: 8 7
v´=24
(3+1)REMPI
State interaction / perturbation j <->V(1S+) / interaction strength

31. 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)

32. 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

33. AB
AB+ + e
AB**
|i1>
|i4>
|i3>
|i2> :
Mechanism of nxhn absorption /
ionization; involvement of
intermediate states. ?

34. W´´=0(S) W´=0(S) W´´=0(S) I µ m12s1 + m32s3 N,T: I µ m32s320
W´´=0(S)
W´=0(S) W´´=0(S)
I µ m12s1 + m32s3
N,T: I µ m32s3
P,R: I µ m12s1 + m32s3
I(N,T) / I(P,R) depend on
m12 and m32 or m12 /m32
Adjust m12 and m32
to obtain best fit:

35. HCl, E(1S+) X(1S+), (3+1)REMPI21
HCl, E(1S+) X(1S+), (3+1)REMPI
m12 /m32 = 0.90±0.15

36. 22
W´´=0(S)
W´=0
(S)
W´=1
(P)
W´´=0(S)
W´=0
(S)
Four
paths:

37. 0.81 0.36 Paths vs m12 and m32 : Major path for HCl: E(1S+)23
X(1S+):
E(1S+)
Major path
for HCl:
Paths vs m12 and m32 :
0.81
0.36
-vs exp.: m12 /m32 = 0.90±0.15

38. 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

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

40. Surface science studies/ collaboration work with J. C
Surface science studies/ collaboration work with J.C. Polanyi, Toronto: Na
effect?
i.e.: 1) hn + NaBrH(s) -> NaBr(s) + H(g)

41. Surface science studies/ collaboration work with J. C
Surface science studies/ collaboration work with J.C. Polanyi, Toronto: Na
effect?
i.e.: 2) hn + NaBrH(s) -> Na(s) + HBr#(g)
detect / measure HBr by REMPI: observe kinetic energy.

42. IREMPI n

43. (3+1)REMPI simpler spectrum / “more convenient” wavelength
2 x (1/l=255nm)
3 x (1/l=382nm)
(3+1)REMPI simpler spectrum / “more convenient” wavelength

45. i.e.: » straight line (3+1)REMPI spectra and s useful to determine
N(J)
25oC
Besta
beina lína
Line fit

46. 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

47. V. Blanchet et al., J. Chem. Phys., 119(7), 3751, (2003):
3dpF1Su+ <-<-<- X1Sg +

48. 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

49. |1> A30+ <- X10+ (v1,v0) Energy |0> AB = CdAr: v1+1 v1 v1-1
r (A-B)

50. [2P1/2]c6s;1g <-<- X 0g
AB = I2:
|1>
v1+1
[2P1/2]c6s;1g <-<- X 0g v1
v1-1
Energy
(v1,v0) v0
|0>
r (A-B)

51. i.e.: AB nxhn – (|1>, |0> )/(v1+i,v0) excitations:
nhn + AB -> AB*
mhn + AB -> AB+ + e- (Ekin = 0) n I s
Exp.
Calc.
DE-10
DE00
DE+10
(v1-1)
(v1)
(v1+1)
nxhn
|0>
|1>
DE10 v1 v0
v1 +1
v1 -1 :
B-O approximation, etc.

52. V0=0
V1=

53. V0=0
V1=

54. Hence: excited states with large(r) internuclear distances can
V0=0
V1=
Hence: excited states with large(r) internuclear distances can
not easily be accessed in “simultaneous” excitation
Use double resonance technique

55. Example: Two-colour optical doule resonance (ODR)
ionization of I2:
(1+1)REMPI
Energy
I2 X 1S+ g
I2* B 3P0 u
[I+I-]* 0 g
I2+ + e
r(I-I)
1´ excitation
((1´+1)+1) REMPI

56. Energy
I2 X 1S+ g
I2* B 3P0 u
[I+I-]* 0 g
I2+ + e
r(I-I)

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

60. : Benedikt G. Waage, MS student
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

61. : Robert J. Donovan, Prof., Edinburgh University, UK 24
Acknowledgments:
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