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)

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 = 78625 ± 2 cm-1 E´(J) = B´J(J+1) – D´J2(J+1)2 n0 = E´(v´=0) – E´´(v´´=0) for

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

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

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

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

16 HBr:

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

HBr: DJ = ±1,.. ,±n; n = odd; DW = 0 16 HBr: DJ = ±1,.. ,±n; n = odd; DW = 0 DJ = 0 ,±2,.. ,±n; n = even DW = 0

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

“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)

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)

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

- “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)”

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

“Difference spectra “(1) / Simulation:

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

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

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´´

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

(2,0)

(2,0)

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

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

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

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

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

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)

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

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

W´´=0(S) W´=0(S) W´´=0(S) I µ m12s1 + m32s3 N,T: I µ m32s3 20 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:

HCl, E(1S+) X(1S+), (3+1)REMPI 21 HCl, E(1S+) X(1S+), (3+1)REMPI m12 /m32 = 0.90±0.15

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

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

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

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

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)

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.

IREMPI n

(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

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

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

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

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

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

[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)

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.

V0=0 V1= 0 1 2 3 4 5

V0=0 V1= 0 1 2 3 4 5

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

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

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

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

: 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

: 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