State-to-state spectroscopy and dynamics of neutrals and ions by photoionization and

photoelectron methods

Cheuk-Yiu Ng

Department of ChemistryUniversity of California, Davis

International Symposium on Molecular Spectroscopy (June 17, 2014)

Delayed Pulsed Field Ionization (PFI)

Laser based Technique (M. Dethlefs and E. Schlag)

M + hM*(n>100)

PFI

M++e-

0.1-5 cm-1

PFI

PFI-PE

PFI-photoion (PFI-PI) or MATI

Long Rydberg state lifetimes >s

PFI-photoelectron (PFI-PE) or ZEKE

Background

Stark shift: 6(F)1/2 cm-1

For PFI: 4(F)1/2 cm-1

Lower F - Higher Resolution

Highest resolution reported:

0.1 cm-1 (FWHM)

Vacuum Ultraviolet Laser Tunable range (7.0-19.0 eV)

Four-wave sum and difference-frequency mixings in rare gases or metal vapors: high efficiency

VUV laser generation by four-wave mixing schemes (7-19.5 eV)

The Simulation of VUV Laser Separation from Fundamentals by Convex Lens

12cm 30cm

8mm

MgF2 Bi-Convex Lens

The surface of Slit

Gas Cell

Rcell (um) RSlit (um) Y(mm)

()

Visible (2) 57.8 443 -17.9 3.4

UV (1) 17.3 512 -19.6 3.7

VUV (2 1 -2) 16.6 119 -25.0 4.7

Y

Images and simulation were done by optical software CODE V

Without using defraction grating: Achievable tunable VUV Intensities upto : 1012-1014/pulse

IR-VUV Photoionization-Photoelectron Apparatus at UC Davis

IR-OPO/OPA 1.6-16 m (15 Hz)

0.25 cm-1 or 0.007 cm-1

VUV laser system 7-19.5 eV (30 Hz)

0.12 cm-1

VUV-PFI-PE spectrum of CCl2=CHCl

Origin band

VUV energy (eV)

9.5 9.6 9.7 9.8

0

1Origin band

v11+

HeI PES

v3+ v4

+ v6+

2v11+

Simulation of PFI-PE spectrum of CH3I+

Accurate IE can be determined by spectral simulation

IE

Parameters needed for simulation: Temperature and relative photoionization cross sections

Ionic ground state

Ground state

+

Fix VUV < IE

Scan IR

t=50 ns

Resolved (v, J)

IR frequency (cm-1)

2960 2965 2970 2975 2980

IR-V

UV

-Pho

toio

n (a

rb. u

nit)

0.0

0.5

1.0

1.5

P branch

R branch

Q

9

6

0

3

4 6

*

*

*

*

**

State-to-state PFI-PE spectrum for CH3I(X, 7=1) by IR-VUV photoionization technique

IR Resolution = 0.25 cm-1 (FWHM)

State-to-state two-Color IR-VUV-PFI-PE Measurements CH3I(7, J=1, 2, 5, 7, and 10) +h(VUV) CH3I(7

+, J+)

CH3I + h(IR)

CH3I(7, J)+ h(VUV)

CH3I(7+, J+) + e-

IE(7 7+)

=76896.0(2) cm-1

PFI-PE resolution= 1.2 cm-1 (FWHM)

Photoionization cross section () vs J+=J+-J

Depend only on J+ (not on J and K) and J+ 6.5

VUV laser velocity-mapped ion- and electron- imaging appartatus

Tunable VUV laser radiation

Molecular beam

Imaging TOF chamberPhotodissociation laser 193 nm

Imaging MCP

Comparison of the threshold photoelectron (TPE) and PFI-PE spectra of C6H5Cl

eV

Ele

ctro

n In

tens

ity

(a.u

.)

Resolution:

E E v = E r

Velocity-map imaging-photoelectron (VMI-PE) image of C6H5Cl at 9.24 eV

Abel transformation

The VMI-TPE method has comparable resolution 1.5-2.0 cm-1 (FWHM) with that of PFI-ZEKE or PFI-PE, but with higher photo-electron collection efficiency.

PFI-ZEKE vs. VMI-TPE

H. Gao, Y. Xu, L. Yang, C.-S. Lam, H. Wang, J. Zhou, and C. Y. Ng, J. Chem. Phys. 135 (22), 224304 (2011).

DC Stark shift

=35 cm-1

=50 cm-1

=61 cm-1

=70 cm-1

=78 cm-1 F=162 V/cm

F=131 V/cm

F=99 V/cm

F=66 V/cm

F=33 V/cm

IE(C6H5Cl)

Stark Shift Calibration

E = 3F cm-1

P. Hemberger, M. Lang, B. Noller, I. Fischer, C. Alcaraz, B.K. Cunha de Miranda, G.A. Garcia, H. Soldi-Lose, The Journal of Physical Chemistry A 115 2225 (2011).

H. Gao, Z. Lu, L. Yang, J. Zhou, C. Ng, J. Chem. Phys. 137 161101 (2012)

VMI-PE spectrum for C3H3+

TPE spectrum of propargyl radical cation (C3H3+)

Assignment of VMI-TPE photoelectron bands for C3H3+

observed in the range of 0-4436 cm-1 above the IE(C3H3)

Vibrational Assignment

Experiment (cm-1) Ab initio theory (cm-1)

This work Ricks et al.(2011)

Huang et. al. (2011)

Botschwina et al. (2011)

28(a1) 524 503 528

7(b1) 883 862 872

5(a1)1133 1222 1132 1123

27(a1) 1750 1724 1744

3(a1)2080 2077 2082 2080

25(a1)2280 2264 2246

35(a1)3410 3395 3369

23(a1)4132 4164 4160

A. M. Ricks, G. E. Douberly, P. v. R. Schleyer, and M. A. Duncan, J. Chem. Phys. 132, 051101 (2010).B. X. Huang, P. R. Taylor, and T. J. Lee, J. Phys. Chem. A 115, 5005 (2011)...P. Botschwina, R. Oswald, and G. Rauhut, Phys. Chem. Chem. 13, 7921-7929 (2011).

High-resolution velocity-map imaging threshold photoelectron (VMI-TPE) measurement of C3H3

+

IE(C3H3) = 8.7025 0.0005 eV

Resolution: 2 cm-1

Laser Ablation Transition Metal Beam Source

Ablation Laser beam on a rotating Fe or Ni or Co rod

Pulsed supersonic beamsfor (Fe, Ni, Co) and (FeC, NiC,

CoC)

Carrier GasHe + CH4

VUV Photoion Spectrum of Fe Fe(3d64s2 5D4)+h Fe(3d64s1)np Fe+(3d7; 4F9/2,4F7/2)+e

hv(VUV) (cm-1)

63000 64000 65000 66000 67000 68000

I(F

e+)/

I(hv

) (

arb

itrar

y un

its)

-2

0

2

4

6

8

10

12

hv(VUV) (Å)

148015001520154015601580

4F9/2

4F7/2

6DJ J=9/2 7/2 5/2 3/2 1/2 4FJ J=9/2 7/2 5/2 3/2

n=10 11 12 32

n=9 10 11 27

IE(Fe)

Fe+(3d64s1 6D9/2)

Fe+(3d7; 4F9/2, 4F7/2)

Two-color VIS-UV laser PFI-PE spectra of VN(X3∆1) to form VN+ (X2∆3/2)

IE(VN)=7.05583±0.00011 eV) vibrational frequency:ω1

+ = 1068.0±0.8 cm-1 and re

+ = 1.529 A

Rotationally resolved state-to-state PFI-PE study of FeC+(X2Δ5/2; v+=0)

Y.-C. Chang, C.-S. Lam, B. Reed, K.-C. Lau, H. T. Liou, and C. Y. Ng, J.

Phys. Chem. (invited), 113, 4242 (2009).

Experiment

Simulation

Experiment

Simulation

Comparison of experimental values and state-of-the-art theoretical predictions for FeC/FeC+

Experimental:

IE[FeC+(X2Δ5/2 FeC(X3Δ3)

= 7.593180.00006 eV

e+ = 927.14 ± 0.04 cm-1

re (Å) = 1.559 Å

D0(Fe+-C) – D0(Fe-C)

= 0.309 ± 0.001 eV

Theoretical: C-MRCI+Q

7.1 eV

944 cm-1

1.557 Å

0.0 eV

Conclusion: Energetic predictions by (state-of-the-art??) ab initio theory need much improvement.

Comparison of the VUV laser photoion and PFI-PE spectra of TiO2

IE(TiO2) = 9.57355 ± 0.00015 eV) vibrational frequencies:ω1

+ = 829.1 ± 2.0 cm-1 and ω2

+ = 248.7 ± 0.6 cm-1

The first high-resolution single-photon VUV-PFI-PE measrement of Transition metal-containing molecules

Rotationally resolved state-to-state VIS-UV laser PFI-PE spectra of VCH(X3∆1) to form VCH+ (X2Σ+)

 

Thermochemical cycles of the VC/VC+ and VCH/VCH+ systems

 

Coupled Cluster Theory

Complete Basis Set Extrapolation

Energetics at CCSD(T)/CBS

Inclusion ofCorrelation

Effects

Zero-Point Vibrational Energy

Spin-Orbit Coupling

Diagonal Born-Oppenheimer

Correction

Higher-Order Correction

Scalar-Relativistic Effect

Core-Valence Correlation

Ultimate level of theory could be

effectively as CCSDTQ(Full)/CBS

HΨ=EΨ

CCSDTQ/CBS IE Predictions of Hydrocarbon Radicals

IE(eV) Experiments Theory Deviation

CH2 10.3864 0.0004 10.382 -0.004

CH3 9.8380 0.0004 9.838 0.000

Lau and Ng, JCP, 122, 224310(2005); JCP, 124, 044323(2006).

CCH 11.645 0.0014 11.652 0.007

CH=CH2

8.468 0.029 8.496 0.040

8.485 0.017-0.010

CH2CH3 8.117 0.008 8.124 0.007

CH2CCH 8.7006 0.0005 8.706 0.006

CH2CHCH2 8.1535 0.0006 8.158 0.004

Hydrocarbons and their Halides

IE(eV) Experiments Theory Deviation

cis-butene 9.12500 0.00019 9.133 0.008

trans-butene 9.12837 0.00025 9.132 0.004

iso-butene 9.22047 0.00025 9.222 0.002

cis-C2H2Cl2 9.65839 0.00025 9.668 0.010

trans-C2H2Cl2 9.63097 0.00025 9.642 0.012

CHCl=CCl2 9.4776 0.00020 9.484 0.006

cis-C3H5Br 9.3162 0.00020 9.332 0.016

trans-C3H5Br 9.2715 0.00020 9.289 0.018

Lau and Ng, Acc. Chem. Res., 39, 823 (2006).

Comparison of the experimental IE values for Fe, Ni, and Co and FeC, NiC, and CoC with prediction of CCSDTQ/CBS IE

calculations in eV. Note IE = Experiment IE – CCSDTQ/CBS IE.

IE(FeC) IE(Fe) IE(NiC)

IE(Ni) IE(CoC)

IE(Co)

Eextrapolated CBS

7.426 7.801 8.253 7.051 7.585 7.402

ECV 0.008 -0.005 0.013 -0.003 -0.019 -0.002

EZPVE 0.005 --- 0.000 0.000 0.002 ---

ESO -0.039 -0.001 0.001 0.041 --- 0.012

ESR 0.144 0.094 0.175 0.555 0.148 0.484

EHOC 0.021 0.011 0.084 0.024 0.024 0.019

CCSDTQ/CBS IE

7.565 7.899 8.356 7.668 7.740 7.915

Experiment IE

7.59318 0.0006

7.9024 0.0006

8.37209

0.00006

7.639836

±0.000006

7.73467

0.0006

7.88101

0.00012

IE = Expt -Theo 0.028 0.003 0.016 -0.028 -0.005 -0.034

.

Experiment: D0(Fe+C) - D0(FeC) = 0.3094 0.0001 eV

Theory: D0(Fe+C) - D0(FeC) = 0.334 eV

Energetics of NiC (1Σ+) and NiC+ (2Σ+)

IE(NiC)

CCSDTQ/CBS 8.356

MRCI+Q 8.00

B3LYP 8.26

Experiments 8.372 05 0.00006

D0(NiC) D0(Ni+C)

CCSDTQ/CBS 0.688

MRCI+Q 0.38

B3LYP 0.37

Experiments 0.732 21 0.00006

Ng and co-workers, JCP, 133 054310(2010);Lau et al. JCP 133, 114304(2010).

D0(Ni−C) − D0(Ni+−C)

= IE(NiC) − IE(Ni)

Comparison with DFT and other ab initio quantum predictions

State-to-state photodissociation Study

State-to-state photodissociation studies by

• VUV laser photodissociation pump

• VUV laser photoionization probe

Goals: To apply on photodissociation

Atmospheric gases CO, N2, NO, O2, CO2 etc.

CO is the second most abundant molecular species after H2 in the interstellar medium. VUV photodissociation study of CO is important to understand the properties of the interstellar medium and O-atom isotope fractionation.

CO photodissociation in the VUV region is still largely unknown.

C(3P) + O(1D)

C(1D) + O(3P) ??

M. Eidelsberg, F. Launay, K. Ito, T. Matsui, P. C. Hinnen, E. Reinhold, W. Ubachs, and K. P. Huber, J. Chem. Phys., 121 (1), 292 (2004).

C(3P) + O(3P)

VUV-VUV pump-probe time-slice VMI-PI experiment

CO + VUV-I → C(3PJ) + O(3PJ) 11.05 eV → C(1D) + O(3PJ) 12.31 eV → C(3PJ) + O(1D) 13.02 eV

C(3PJ) + VUV-II C+ + e-

C(1D) + VUV-II C+ + e-

Nd:YAG

Kr or Xe

Nd:YAG

Kr or Xe

E-L valve

CCD

MB

MCP

Phosphor screen

Computer

LiF window

VUV-I

VUV-II

ω 1

ω 2 BBO

BBO

ω 1

ω 2

Dye laser

Dye laser

Dye laser

Dye laser

Nd:YAG

Kr or Xe

Nd:YAG

Kr or Xe

E-L valve

CCD

MB

MCP

Phosphor screen

Computer

LiF window

VUV-I

VUV-II

ω 1

ω 2 BBO

BBO

ω 1

ω 2

Dye laser

Dye laser

Dye laser

Dye laser

State-selective photoionization detection:

1. VUV-UV (1+1’) photoinization detection

2. VUV-excited Autoionizing Rydberg detection

(a) (b): R(0) line of (4pσ)1Σ+(v'=3) at 109484.7 cm-1

(c) (d): R(0) line of (4sσ)1Σ+(v'=4) at 109452.5 cm-1

R. Visser, E. F. van Dishoeck, and J. H. Black, Astron. Astrophys. 503 (2), 323 (2009).

Branching Ratio measurement

Above Dissociation limit of CO

Dissociation into the

channel C(1D)+O(3P)

Fine structure distributions of O(3P0,1,2) and C(3P0,1,2)

VUV-UV(1+1’) photoionization method

VUV-Excited Autoionizing Rydberg VUV-EAR detection method

CO + VUV

C(3P) + O(1D)

C(3P) + O(3P)

C(3P0) + O(1D) -------- (BR-I)*(F0)

C(3P1) + O(1D) -------- (BR-II)*(F1)

C(3P2) + O(1D) -------- (BR-III)*(F2)

C(3P0) + O(3P) -------- [1-(BR-I)]*(F0)

C(3P1) + O(3P) -------- [1-(BR-II)]*(F1)

C(3P2) + O(3P) -------- [1-(BR-III)]*(F2)

BR-I = [C(3P0) + O(1D)] / { [C(3P0) + O(3P)] + [C(3P0) + O(1D)] }

BR-II = [C(3P1) + O(1D)] / { [C(3P1) + O(3P)] + [C(3P1) + O(1D)] }

BR-III = [C(3P2) + O(1D)] / { [C(3P2) + O(3P)] + [C(3P2) + O(1D)] }

F0 = [C(3P0)] / {[C(3P0)] + [C(3P1)] + [C(3P2)]}

F1 = [C(3P1)] / {[C(3P0)] + [C(3P1)] + [C(3P2)]}

F2 = [C(3P2)] / {[C(3P0)] + [C(3P1)] + [C(3P2)]}

BR-I BR-II BR-III

(4sσ)1Σ+(v=4) 0.62±0.03 0.09±0.01 0.08±0.01

(4pσ)1Σ+(v=3) 0.37±0.02 0.03±0.02 0.12±0.01

(4pπ)1Π(v=3) 0.20±0.01 0.59±0.03 0.13±0.01

C(3P2)+O(1D) C(3P1)+O(1D) C(3P0)+O(1D) C(3P2)+O(3PJ) C(3P1)+O(3PJ) C(3P0)+O(3PJ)

(4sσ)1Σ+(v=4) 1.7±0.3 0.9±0.2 42.4±3.0 19.3±2.0 9.1±1.9 26.6±2.3

(4pσ)1Σ+(v=3) 2.7±0.4 0.7±0.4 19.7±1.6 19.3±1.9 23.3±2.3 34.3±2.2

(4pπ)1Π(v=3) 4.3±1.1 23.4±3.4 5.5±0.9 27.7±4.8 16.6±2.7 22.5±3.3

Correlated fine structure distribution of the channel C(3P0,1,2)+O(1D2)

Thank you:

Greetings from Ng Group 2013