Why multiphoton exitations(?); advantages/disadvantages One color experiments / data Experimental methods: Multiphoton ionization (MPI & REMPI) Data interpretations

•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

79.00x103 78.8078.7078.6078.5078.40

3xh / cm-1

N

O

PR

S

T

Calc.

Exp.

Q

(3+1) REMPI HBr

Simulation:

i(32) <- X(1+)(0,0)

79.00x103 78.8078.7078.6078.5078.40

3xh / cm-1

N

O

PR

S

T

Calc.

Exp.

Q

(3+1) REMPI HBrSimulation:

Be´/ Bf´ = 7.975/7.969 ±0.030cm-1

De´/Df´= (0.55/0.50 ± 0.10)x10-3 cm-1

0 = 78625 ± 2 cm-1

E´(J) = B´J(J+1) – D´J2(J+1)2 0 = E´(v´=0) – E´´(v´´=0) for

i(32) <- X(1+)(0,0)

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

(2+1) REMPI spectra of I2:

(v1,v0)

Fig. 2

Calc. Exp.(2+1) REMPI spectra of I2:as well as Rotational line series:O: J-2 <- J; P: J-1 <- JQ: J <- JR: J+1 <- J; S: J+2 <- J

/ cm-1

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

(v1,v0) =

Fig. 3OP

i.e.:

AB

AB+ + e

AB**

|i1>

|i4>|i3>

|i2>

:

Properties of AB* and AB:- energy configurations- molecular geometries





78.2x103 78.178.077.977.877.777.6

3xh / 2xh (cm-1

)

0

013

7

N(J-3)P(J-1) R(J+1)

T(J+3)4

J=6

E(´=0)<-X(´´=0),(0,0)

38

09

0 J=8S(J+2)Q(J)

O(J-2)(2+1)REMPI

(3+1)REMPI

HBr:

16

z

L

NLJL

= 0

Total angular momentum changesFor ´=0 ´´=0:

J:QJ-1;P J+1;RJ-3;N J-2;O J+2;S J+3;T

JJ = 1

J = 1

J = 1

78.2x103 78.178.077.977.877.777.6

3xh / 2xh (cm-1

)

0

013

7

N(J-3)P(J-1) R(J+1)

T(J+3)4

J=6

E(´=0)<-X(´´=0),(0,0)

38

09

0 J=8S(J+2)Q(J)

O(J-2)(2+1)REMPI

(3+1)REMPI

HBr:

J = 1,.. ,n; n = odd; = 0 J = 0 ,2,.. ,n; n = even = 0

16





83.0x103 82.982.882.7

3xh / cm-1

R

S

T

Q

P

ON

0

7

4

calc.

exp.HBr, (3+1)REMPI´=3( ´´=0(

18

B´= 8.39cm-1

D´= (0.85x10-3cm-1

0 = 828373 cm-1

2xh3xh

3xh

´=3() ´=2() ´=1() ´=0()

´´=0()

i 1xh 2xh 3xh

“New” state, not detected before:

Predicted state ((23)5d) in this region: L13 (0 = ?????)

“New” state: L13 (0 = 828373 cm-1)

19





Complicated spectra, analyses / Example I:

HCl, (3+1) REMPI:

cm-1

3 x (1/=333 nm)

HCl, (3+1) REMPI / Simulation:

cm-1

OK OK???!!

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

???!!???!!

cm-1

exp. – calc./“Diff.sp.(1)”

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

exp.

calc.

HCl, (3+1) REMPI

-

3 x (1/=333 nm)

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

“Difference spectra “(1) / Simulation:

58.0x10

3 57.957.857.7

3hcm-1

NO, (3+1)REMPI

D2 X2

REMPI-Current298 K

REMPI-TOFjet cooled

(2,0) -band

Complicated spectra, analyses / Example II:

X 2:

NO

D 2:

z

NL

L

L L

JL

NL

LL

L

JL

z

= 3/2 = 1/2

Spin-rot.interaction

Spin-orbitinteraction

Orbit-rot.interaction

NL

S

NL

S

JLJL

z

E1´

E1´´ E2´´

Av´´=0

Spin-rot.interaction

Orbit-rot.interaction

E2´

Cv´´=0

Cv´

(2,1)

(1,2)(1,1)

(2,2)

4002000-2003h/ cm

-1

three-photon absorptionD<-<-<-X, NON,O,P,Q,R,S,T

(1,1)

(2,1)

(1,2)

(2,2)

"Stick spectrum"

Calc.

, T=298K

(11) (22)

(21)(12)

2

2

(2,0)

57.90x103 57.8557.8057.7557.7057.65

3xh/ cm-1

NO (3+1)REMPI-Current

D2 X

2 simulationT = 298 K

Exp.

Calc.

(2,0)

57.90x103 57.8557.8057.7557.7057.65

3xh/ cm-1

NO, (3+1)REMPI-TOF

D2 X2 simulation

T = 80K

Exp.

Calc.

(2,0)





AB

AB+ + e

AB**

|i1>

|i4>|i3>

|i2>

:

State interactions/AB** <->AB#

&dissociation processesAB** -> A# + B#

?

AB#/A#+B#

89.789.689.589.489.389.289.189.0x10

3

HCl(3+1) j3-(0

+) (0,0)

B´=9.654, D´=-0.00039 0=89282

P R

Exp.

Calc.

1357J''=9

0 1 2 34

65 7 89 J''

0 1 2 3=J''

T

HCl; (3+1)REMPIj30

- <- X1+

(0,0)

?

?(3+1)REMPI

j30- <- X1+

(0,0)

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

?

92.0x103

91.5

91.0

90.5

E/c

m-1

300250200150100500EJ´,J´+1/cm

-1

5

6

7

8

9

10

11

EJ´,J´+1/cm-1

(2+1)REMPI,HCl(Q)

from (2+1)REMPI,HCl(Q)

from (3+1)REMPI,HCl(R)

5

6

7

8

9

10

11-12.6.2001, HCl,IGOR file:"aHCl(3+1)j3S(0)Calc"AK/PC2

5

V state

j state

(3+1)REMPI

explanation:

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

v´=24

7

8

Rotational perturbation observed in vibrational band due to the transition2P3/2c5s;1g <-<- X 0g,v1 = 0, v0 = 1

::Because of state interactions:

2P3/2c5s;1g <-> D´(2g)





AB

AB+ + e

AB**

|i1>

|i4>|i3>

|i2>

:

Mechanism of nxh absorption / ionization; involvement ofintermediate states.

?

´´=0()

´=0() ´´=0()

P,R: I 12s1 + 3

2s3

N,T: I 32s3

I(N,T) / I(P,R) depend on1

2 and 32 or 1

2 /32

Adjust 12 and 3

2

to obtain best fit:

20

I 12s1 + 3

2s3

21

83.9x103 83.883.783.683.583.483.3

3h/cm-1

TNR

P

Exp.

Calc.

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

12 /3

2 = 0.900.15

2,,,,,,,,,,,,,,,2

1 43325

1

2,,,,,,,,,,,,23 2

22

´´=0()

´=0()Four

paths:

,,,,

, ,,

,

´´=0()

´=0()

´=1()

23

Paths vs 12 and 3

2 :

0.81

0.36

0.36

0.36

23

,,,

259

,,,

25

81

,,,

25

9

,,,

25

9

,,,1

,,,4

,,,1

,,,1

21 2

323 /

-vs exp.: 12 /3

2 = 0.900.15X(1+):

E(1+)

Major path

,

,,

for HCl:





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

Na

HBr

Na

effect?

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


Na

effect?

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

detect / measure HBr by REMPI: observe kinetic energy.


IREMPIjjiiREMPI ssI 22

)(JNIREMPI

/)(

)(

REMPI

REMPI

IJN

JNI

CJEkTJ

I

kT

JEJJN

REMPI

)(1

)12(ln

))(

exp()12()(

:ondistributiBoltzmann

m/equilibriu at thermal

79.00x103 78.9078.8078.7078.6078.5078.40

2xh/3xh [cm-1

]

29 Q

1 R 10

(2+1)REMPI 10 3P

9S8 O

(3+1)REMPI

T0 8

HBr

2 x (1/=255nm)

3 x (1/=382nm)

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

79.00x103 78.8078.7078.6078.5078.40

3xh / cm-1

N

O

PR

S

T

Calc.

Exp.

Q

(3+1) REMPI HBr

-4

-3

-2

-1

0

ln(I

(J)/

S(J)

)

6004002000E(J) / cm

-1

O

P

Q

R

S

T

CJEkTJ

IREMPI

)(1

)12(ln

i.e.:

straight line

(3+1)REMPI spectra and useful to determine N(J)

25oC

Besta beina lína

Line fit





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

3dF1u+ <-<-<- X1g

+





r (A-B)

Ene

rgy

v0

v1

v1-1

v1+1

AB = CdAr:

A30+ <- X10+

(v1,v0)

r (A-B)

Ene

rgy

v0

v1

v1-1

v1+1

AB = I2:

(v1,v0)

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

AB nxh – (/(v1+i,v0)excitations:

nh + AB -> AB*mh + AB -> AB+ + e- (Ekin = 0)

i.e.:

201 EM

nxh

E10

v1

v0

v1 +1

v1 -1

:::

2

01 d

vv

B-O approximation, etc.

I

Exp.

Calc.

E-10 E00 E+10

(v1-1)

(v1)

(v1+1)

80x103

60

40

20

0

E [c

m-1

]

2.01.81.61.41.21.0R [Å]

300

250

200

150

100

50

Inte

nsity

64x103

6260585654Frequency [cm^-1]

80x103

60

40

20

0

E [c

m-1

]

2.01.81.61.41.21.0R [Å]

600

500

400

300

200

100

0

Inte

nsity

64x103


80x103

60

40

20

0

E [c

m-1

]

2.01.81.61.41.21.0R [Å]

1000

800

600

400

200

0

Inte

nsity

64x103


V1= 0 1 2 3 4 5V0=0

80x103

60

40

20

0

E [c

m-1

]

2.01.81.61.41.21.0R [Å]

500

400

300

200

100

Inte

nsity

64x103


80x103

60

40

20

0

E [c

m-1

]

2.01.81.61.41.21.0R [Å]

150

140

130

120

110

100

90

Inte

nsity

64x103


80x103

60

40

20

0

E [c

m-1

]

2.01.81.61.41.21.0R [Å]

60

50

40

30

20

10

Inte

nsity

64x103


V1= 0 1 2 3 4 5V0=0

80x103

60

40

20

0

E [c

m-1

]

2.01.81.61.41.21.0R [Å]

6

4

2

Inte

nsity

64x103


80x103

60

40

20

0

E [cm

-1]

2.01.81.61.41.21.0R [Å]

30x10-3

25

20

15

10

5

0

Inte

nsity

64x103


V1= 0 1 2 3 4 5V0=0

•Hence: excited states with large(r) internuclear distances cannot easily be accessed in “simultaneous” excitation• Use double resonance technique

Example: Two-colour optical doule resonance (ODR) ionization of I2:

Ene

rgy

I2 X 1S+ g

I2* B 3P0 u

I+I-* 0 g

I2+ + e

r(I-I)

(1+1)REMPI

1´ excitation

((1´+1)+1) REMPI

Ene

rgy

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/

24

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

Funds:•Icelandic Science foundation•University Research Fund•NORFA / NORDPLUS

Collaborators: :Robert J. Donovan, Prof., Edinburgh University, UKTimothy G. Wright, University of Sussex, UKLars Madsen, Aarhus, DenmarkNORFA network participants (?)

Acknowledgments:

Documents

Why multiphoton exitations(?); advantages/disadvantages One color experiments / data Experimental methods: Multiphoton ionization (MPI & REMPI) Data interpretations