MASS-ANALYZED THRESHOLD IONIZATION SPECTROSCOPY

OF Sc OXIDE CLUSTERS .

Sergiy Krasnokutski, Changhua Zhang and Dong-Sheng Yang

University of Kentucky, Lexington, KY 40506, USA

$ National Science Foundation $

TOF of ScxOy clusters

Background

Common TOF in metal-ligand complex studies4

62

99

123

141

152

160

170 19

7

0 50 100 150 200

Rel

ativ

e in

tens

ity

Mass (amu)

0 100 200 300 400 500 600 700 800 900 1000

Rel

ativ

e in

tens

ity

Mass (amu)

Time of flight of the ions could be measured and related to their mass, and therefore a mass-selective spectrum could be obtained – hence the name mass-analysed threshold ionization (MATI).

Advantages of MATI compare with ZEKE

Disadvantages of MATI compare with ZEKE

Background electrons are very rapidly dispersed in the ZEKE experiment by very small discrimination fields, the ions move more slowly and remain in the excitation region for much longer. MATI spectra have generally been of lower resolution than ZEKE spectra.

Background

HV

M CP

TP 400L/s

TP 400L/sDP 2300L/s

Extraction Cans

Tim e of Flight Tube

M etal

G ateValve

Sk immer

H e 30 p si

P u lsed Va lve

53 2 n m

M eta l R od

ZEKE or MATI experimental setup

0 50 100 150 200 250 300

Vo

ltag

e

Time (ns)

Inhomogeneous field in MATI experiment

CAN2 = +2500 VCAN1 = +1700 V

320 V/cm-1

Laser pulse

2-5s

Time

1

41100 41120 41140 41160 41180 41200

18 cm-1

Wavenumber (cm-1)

1.66 V/cm

1.33 V/cm

1 V/cm

5 cm-1ZEKE

MATI, Sc-C7H8, spoil field dependence

=3.6*F1/2= 2 *F1/2= 5 *F1/2

1

Inhomogeneous field in MATI experiment

CAN2 = +2500 VCAN1 = +1700 V

320 V/cm-1

Laser pulse

2-5s

Time

1

2

0 50 100 150 200 250 300

Vo

ltag

e

Time (ns)

22160 22200

Re

lativ

e in

ten

sity

Wavenumber (cm-1)

22174

22172.5MATI

ZEKE

5.5

6.5

MATI and ZEKE of V3 cluster2

0 100 200 300 400 500 600 700 800 900 1000

Re

lativ

e in

ten

sity

Mass (amu)

Mass spectrum of ScxOy clusters

Ionization laser frequency 45450 cm-1

0 100 200 300 400 500 600 700 800 900 1000

Sc2O

2

Mass (amu)

Re

lativ

e in

ten

sity

Mass spectrum of ScxOy clusters

Ionization laser frequency 45450 cm-1

Sc2O2 experimental / B3LYP simulation

-400 -300 -200 -100 0 100 200 300 400 500 600 700 800

Re

lativ

e in

ten

sity

Wavenumbers (cm-1)

422 cm-1 714 cm-1

2Ag 1Ag

2Ag 3B1U

IE= 44967 cm-1

0 200 400 600 800 1000

Re

lativ

e in

ten

sity

Mass (amu)

Sc3O

4

Mass spectrum of ScxOy clusters

Ionization laser frequency 37600 cm-1

E (cm-1) 0 15392 21255

Stable structures of Sc3O4

-200 0 200 400 600 800 1000 1200 1400

Re

lativ

e in

ten

sity

Wavenumber (cm-1)

Sc3O4 experimental / B3LYP simulation

Experiment, He

Experiment, Ar

IE= 35937 cm-1

Simulation, 300K

Simulation, 100K

1A1 2A1

1A1 2A1

-200 0 200 400 600 800 1000 1200 1400 1600

Re

lativ

e in

ten

sity

Wavenumber (cm-1)

440

Vibrational modes of S3O4

668

274

204

300

754

IE= 35937 cm-1

• The method to study cluster formation was developed

• This method was applied to study growth of scandium oxide clusters

• The Sc2O2 is the main building block for the

larger clusters

Conclusions