High-resolution Fourier transform emission spectroscopic study of the molecular ions

Feb. 22. 2005Feb. 22. 2005

High-resolution Fourier transform emission High-resolution Fourier transform emission spectroscopic study of the molecular ionsspectroscopic study of the molecular ions

Yoshihiro NakashimaYoshihiro Nakashima

Contents Contents

1. General introduction1. General introduction

2. 2. BB 22++ – – XX 22++ transition of the PN transition of the PN++ ion ion

3. 3. AA 22 – – XX 22 transition of the OCS transition of the OCS++ ion ion

4. 4. AA 22++ – – XX 22 transition of the BrCN transition of the BrCN++ ion ion

General introductionGeneral introduction

1. General introduction1. General introduction

2. 2. B B 22++ – – X X 22++ transition of the PN transition of the PN++ ion ion

3. 3. A A 22 – – X X 22 transition of the OCS transition of the OCS++ ion ion

4. 4. A A 22++ – – X X 22 transition of the BrCN transition of the BrCN++ ion ion

Chapter 1Chapter 1

Molecular ion (cationic species)Molecular ion (cationic species)

Terrestrial and extraterrestrial Terrestrial and extraterrestrial environmentsenvironments

flameplasmaplanetary atmosphere cometinterstellar space etc….

Protonated ionProtonated ionmolecule + proton (H+)

closed shell

ex) H3O+, NH4+, H3

+ …

Radical ionRadical ionionization of molecule

open shell

ex) N2+, CO2

+, HCCH+ …

Spectroscopic study Spectroscopic study

Ion - molecule reaction Ion - molecule reaction

Spectroscopic study of the radical ion Spectroscopic study of the radical ion

Photoelectron spectroscopy Photoelectron spectroscopy

Laser spectroscopy Laser spectroscopy MPI or REMPI + LIF or photodissociation

Cavity ringdown etc…

Matrix isolation spectroscopy Matrix isolation spectroscopy

present studypresent study

Fourier transform spectrosocpy (FT) Fourier transform spectrosocpy (FT)

Flowing afterglow technique Flowing afterglow technique

Electronic energy of ion

High-sensitive detection

x

M1

M2

B.S.

S

D

Fourier transform spectrosocpy (FTS)Fourier transform spectrosocpy (FTS)

Interferogram Interferogram FF((xx))

F(x)

Spectrum Spectrum BB(())

FT

Michelson interferometerMichelson interferometer

x : path difference

: wavenumber

Fourier transform spectrosocpy (FTS)Fourier transform spectrosocpy (FTS)

High-resolution spectroscopy ( depend on x )

Determination of accurate frequency

Wide spectral range ( 10 – 45,000 cm-1 for Brucker IFS120HR )

Low signal to noise ratio Low signal to noise ratio

Production method of transient species Production method of transient species with high concentration and low noise… with high concentration and low noise…

Flowing afterglow technique Flowing afterglow technique

Flowing afterglow Flowing afterglow

Electronic energy level of He

He ( 2He ( 211SS ) : ) : 20.61 eV, 20.61 eV, = 19.7 ms = 19.7 ms

He ( 2He ( 233SS ) : ) : 19.81 eV, 19.81 eV, ～ ～ 150 min150 min

1eV = 96. 5 kJ/mol

De(N2) = 946 kJ/mol

1 1S

2 1S

2 1P

3 1S3 1P

2 3S

2 3P

3 3S3 3P

0

18

19

20

21

22

23

24

eV

HeI

metastable

The reaction of The reaction of molecule with metastablemolecule with metastable

Flowing afterglowFlowing afterglow Penning ionization

He ( 1He ( 111SS ) ) He* ( 2He* ( 233SS oror 2 211SS))

He*He* + M M*M* + He ( 1He ( 111SS ) )

M*M* ( M( M++ )* )* + ee--

( M( M++ )* M )* M++ + + hh

He* + M ( MHe* + M ( M++)* + He + e)* + He + e--

Penning ionization optical Penning ionization optical spectroscopy ( PIOS )spectroscopy ( PIOS )

1. low noise 1. low noise

2. stable emission 2. stable emission

3. selective production of the ion 3. selective production of the ion

A A 22 – – X X 22 transition of OCS transition of OCS++

1. General introduction1. General introduction

2. 2. B B 22++ – – X X 22++ transition of the PN transition of the PN++ ion ion

3. 3. A A 22 – – X X 22 transition of the OCS transition of the OCS++ ion ion

4. 4. A A 22++ – – X X 22 transition of the BrCN transition of the BrCN++ ion ion

Chapter 3Chapter 3

Introduction Introduction

R(OCS)

11

15

20

eV

X 2

A 2B 2+

4

v = 0

v = 0

M. J. Hubin-Frank et al. ( MCSCF-CI )

Isovalent with CO2+ and CS2

+

Predissociation in A 2

1. repulsive 4

2. Internal conversion from A 2 to X 2

Spectroscopic study is few!Spectroscopic study is few!

Previous worksPrevious works

1. Oschner Oschner et al.et al.

LIF spectra of the (000)(000)(000) band(000) band

of the 2 2 3/2 3/2 X X 22transition.

3. Weinkauf and BoeslWeinkauf and Boesl Photodissociation spectra of the (000)(000)(000) band(000) band of the 2 2 1/2 1/2 X X 221/21/2transition.

4. C. L. Lugez et al. Infrared absorption Infrared absorption spectrum in Ne matrix.Ne matrix.

2. Kakoschke et al. Photodissociation spectra of the AA2 2 X X 22andBB2 2 ++

X X 22transitions.

A 2

X 2

B 2+

39,180

31,400

0

cm-1

=3/2

=1/2

=3/2

=1/2

Experimental Experimental

He (2.5 Torr)

OCS (2-3 mTorr)

resolution : 0.03 cm-1

spectral region : 20,000 – 28,000 cm-1

accumulation time : 60 hrs.

Penning ionizationHe*(23S) + OCS OCS+ + He(11S)

(I.P.=11.19 eV)

Observed spectrumObserved spectrum

cm-1

He

S+CO+ (2,1) CO+ (1,0) CO+ (2,0)

CO+ (3,0) CO+ (4,0)

He

OCS+ OCS+

OCS+

OCS+

A A 22 – – X X 22 transition of OCS transition of OCS++

(000)-(002)(000)-(003)

(000)-(004)(000)-(005)

33 (CO str.) progression (CO str.) progression

cm-1

A A 22 – – X X 22 transition transition

P (J’’)R (J’’)

58.5 50.5 40.5 30.5 20.5 10.5

65.5

FWHM : 0.05 cm-1

Trot : 300 K

A A 22 – – X X 22 transition transition

QJ’’=2.55.5

PJ’’=1.5 5.5

R

66.5 60.5R

R (1.5) and P(2.5)

Weak Q branch

A A 22 – – X X 22 transition transition

A A 22 – – X X 22 transition transition

P (J’’)R (J’’)

46.5 40.5 30.5 20.5 10.5 10.56.5 0.5

FWHM : 0.05 cm-1

Trot : 300 K

A A 22 – – X X 22 transition transition

parity

+ parity J’’=23.5J’’=26.5

– –type doublingtype doubling

A A 22 – – X X 22 transition transition

P-branch

state constant =3/2 =1/2 A 2 T000 31404.1021(25) 31145.3089(99) B000 0.186823(12) 0.187396 (29) 107D000 0.395(24) 0.395 p/2 +q 0.0008(11)

X 2 3 2089.8512(80) 2085.6308(30) x33 19.7997(66) 19.7997 y333 0.5097(18) 0.5097 z3333 0.01016(16) 0.01016

B000 0.194634(13) 0.194805(28) 107D000 0.619(32) 0.561(21) 103 3 0.6432(20) 0.6136(51) 108 3 0.327(53) 0.327 105 33 0.106(33) 0.106 p/2 +q 0.0040(10)

Molecular constantsMolecular constants (unit : cm(unit : cm-1-1))

Discussion Discussion

parameter X 2 A 2 X 1+

1 (CS str.) present study 690 815 previous study 695.7 804.8 858.95 ab initio 697 843 904

3 (CO str.) present study 2087.741 previous study 2071.1 2036 2062.22 ab initio 2166 2282 2161

Harmonic frequencyHarmonic frequency

11 (CS str.) : (CS str.) : 11 = ( 4 = ( 4BBee33//DDee

))1/21/2

33 (CO str.) : ( (CO str.) : ( 333/23/2 + + 33

1/21/2 ) ) 22

Rotational constantsRotational constants

=3/2

=1/2Oschner et al

Weinkauf and Boesl

B000 = B000 (1 + B000/A)3/2

B000 = B000 (1 B000/A)1/2

BB000000((XX) = 0.194719(15) ) = 0.194719(15) cmcm-1-1

BB000000((AA) = 0.187110(16) ) = 0.187110(16) cmcm-1-1

B00v = B000 3v + 33v2

Spin-orbit interaction constantsSpin-orbit interaction constants

X 2

A 2

2

2

2

2B000 = B000 (1 + B000/A)3/2

B000 = B000 (1 B000/A)1/2

|T000 – T000| = |A’ – A’’|1/23/2

AA ((XX) = ) = 380.9(66) 380.9(66) cmcm-1-1

A A ((AA) = ) = 122.2(66) 122.2(66) cmcm-1-1

122.2

380.9

(A’ = 111.8)

(A’’ = 367.2)

Bond length of OCSBond length of OCS++

parameter X 2 A 2 X 1+

rCO (A) present study 1.104 1.253 previous study 1.136 1.252 1.16021 ab initioa 1.129 1.267 1.157

rCS (A) present study 1.657 1.589 previous study 1.634 1.606 1.56014 ab initioa 1.657 1.589 1.571

a : K. Takeshita et al. (MRSD-CI)

(8)2 (9)2 (2)4 (3)3 : X 2

(8)2 (9)2 (2)3 (3)4 : A 2

3 : S 3p (non-bonding)

2 : CO (bonding)

SummarySummary 1. Ultraviolet emission spectrum of the A 2 - X 2 transition of the OCS+ ion was observed by FT spectroscopy.

2. Rotational analysis of the seven bands, A 23/2 (000) - X 2 (00v) ( v=0, 2-5 ) and A 2 (000) - X 2 (00v) ( v=3 and 4 ) transitions, were performed to determine the molecular constants.

3. Spin-orbit interaction constants A and the harmonic frequencies 1 and 3 of A 2 and X 2 were determined.

4. The geometrical difference between X 2 and A 2 was indicated, which was explained by the electronic configuration.

A A 22++ – – X X 22 transition of BrCN transition of BrCN++

1. General introduction1. General introduction

2. 2. B B 22++ – – X X 22++ transition of the PN transition of the PN++ ion ion

3. 3. A A 22 – – X X 22 transition of the OCS transition of the OCS++ ion ion

4. 4. A A 22++ – – X X 22 transition of the BrCN transition of the BrCN++ ion ion

Chapter 4Chapter 4

BrCNBrCN++ ion ion

Renner-Teller effectRenner-Teller effect

Splitting of the vibronic state by the excitation of the bending vibration

Electronic ground state : X X 22

spin-orbit interaction

IntroductionIntroduction

Vibronic interaction Vibronic interaction

V+ = a ( 1 + ) (r)2 + …

V- = a ( 1 – ) (r)2 + …

||<1 ||>1

NCO, NNCO, N22OO++ ( ( X X 22)) NHNH22

( ( X X 22BB11 , , A A 22))

: Renner parameter: Renner parameter

Bending potential functionBending potential function

Large spin-orbit interactionLarge spin-orbit interaction

A A = = 1477 cm1477 cm-1-1

1477cm-1

IntroductionIntroduction

Influence of the spin-orbit interactionspin-orbit interaction on the Renner-Teller effectRenner-Teller effect

22 = 287.24(20) cm = 287.24(20) cm-1-1 287.24 cm-1

Previous worksPrevious works

2. M. A. Hanratty et al. LIF spectra of the B B 2 2 3/23/2X X 2 2 3/23/2 transition

4. C. Salud et al. Infrared diode laser spectroscopy of the 11 (CN str.) fundamental band(CN str.) fundamental band of the X X 2 2 3/23/2state

1. J.Fulara et al.

Low-resolution emission spectra

of the B B 2 2 3/23/2 XX 2 2 3/23/2 and

A A 2 2 X X 2 2 transitions

A 2+

X 2

B 2

0

13,700

19,230

cm-1

(001)(002)

(012)

(100)

3. M. Rosslein et al. LIF spectra of the B 2 3/2X 2 3/2 transition to determine the rrss-structure-structure of BrCN+

ExperimentalExperimentalHe (1.0 Torr)

BrCN (2-3 mTorr)

resolution : 0.02 cm-1

spectral region : 11,500 – 15,000 cm-1

accumulation time : 40 hrs.

Penning ionizationHe*(23S) + BrCN BrCN+ + He(11S)

(I.P.=12.08 eV)

Observed spectrum ( Observed spectrum ( A A 22+ + - - X X 22 ) )

(010)-(000)

(010)-(010)

(000)-(000)

(001)-(011)(000)-(010)

(010)-(001)(100)-(100)

(001)-(001)

(000)-(100)

=3/2

=1/2 (000)-(000)

(010)-(010)(001)-(001)

(000)-(010)

A A 22+ + (000) - (000) - X X 223/2 3/2 (000) transition (000) transition

P1 R21

P21 + Q1 R1 + Q21

A A 22+ + (000) - (000) - X X 223/2 3/2 (000) transition(000) transition

P1 branch79BrCN+ J’’=35.5J’’=39.5

81BrCN+ J’’=35.5J’’=39.5

A A 22+ + (000) - (000) - X X 221/2 1/2 (000) transition(000) transition

P2 + Q12 R12 + Q2

P12 R2

Molecular constants Molecular constants (unit : cm(unit : cm-1-1))

state constant FT + D.L. D.L. LIF

A 2 + 3/2 13697.1192(13) B 0.1411698(51) 107D 0.346(16) 0.017752(37)

X 2 B3/2 0.1414036(47) 0.1413799(41) 0.141536(47) 107D 0.307(15) 0.158(23) 0.86(28)

state constant FT + D.L. D.L. LIF

A 2 + 3/2 13697.1613(13) B 0.1403581(50) 107D 0.299(16) 0.017672(37)

X 2 B3/2 0.1405939(47) 0.140582(11) 0.140859(86) 107D 0.262(14) 0.147(60) 1.5(56)

79BrCN+

81BrCN+

eff

eff

AA 22++(000) – (000) – XX 223/23/2(000) transition(000) transition

Molecular constants Molecular constants (unit : cm(unit : cm-1-1))

state constant 79BrCN+ 81BrCN+

A 2 + 1/2 12220.6523(46) 12220.6762(59) B 0.14117a 0.14036a 107D 0.346a 0.299a

0.0178a 0.0177a

X 2 B1/2 0.1416173(62) 0.1407575(67) 107D 0.347(11) 0.214(16) p/2 + q 0.00600(11) 0.00501(15)

eff

79B000 = 0.1415105(32) cm-1

81B000 = 0.1406757(41) cm-1

Rotational constantRotational constant B B000000

B3/2 = B000 ( 1 + B000 /A )

B1/2 = B000 ( 1 B000 /A )

eff

eff

AA 22++(000) – (000) – XX 221/21/2(000) transition(000) transition

Spin-orbit interaction constant Spin-orbit interaction constant

A = 1/2 – 3/2

79A = 1476.4669(48) cm-1

81A = 1476.4841(60) cm-1X 2 (000)

A 2+ (000)

X 2

X 2

3/2 1/2

A

low resolution emission spectroscopy

A = 1477 cm-1

rr00-structure -structure

I = mkzk2

0 = mkzk

I = zBr2

mBr mk

mBr + mk

Br C N×

zBr

zC

zN

G

species electronic state rBrC rCN

BrCN X 1 + 1.789 1.158

BrCN+ X 2 1.788(54) 1.103(78) 1.745(7) 1.195(8)

A 2 + 1.814(61) 1.064(90)

unit : A

A A 22+ + - - 22 transitiontransition

P2 R2

P12 R12

A A 22+ + - - 22 transitiontransition

P1 R1

P21 R21

Molecular constants Molecular constants (unit : cm(unit : cm-1-1)) state constant 79BrCN+ 81BrCN+

A 2 + 13410.1135(12) 13410.2424(17) B 0.14117a 0.14036a 107D 0.346a 0.299a

0.0178a 0.0177a

2 B 0.1419339(19) 0.1411504(26) 107D 0.3165(60) 0.3493(79) p 0.020312(27) 0.020187(32)

A2+ -2

state constant 79BrCN+ 81BrCN+

A 2 + 11921.6949(21) 11921.8374(25) B 0.14117a 0.14036a 107D 0.346a 0.299a

0.0178a 0.0177a

2 B 0.1420853(25) 0.1412934(28) 107D 0.3035(58) 0.3139(66) p 0.018749(46) 0.018563(52)

A2+ -2

A 2+(000)

X 2(010)

2

2

2r

DiscussionDiscussion

Rotational constants Rotational constants BB010010

79B010 = 0.1420111(23) cm-1

81B010 = 0.1412625(25) cm-1

B = B010 [ (B010 – /2) cos 2 ]2/2r B = B010 [ (B010 – /2) cos 2 ]2/2r

: spin-rotation interaction constant

Parameter Parameter rr

2r = [ Aeff2 + 4(2)2 ]1/2

= -

279r = 1488.4186(24) cm-1

281r = 1488.4050(30) cm-1

Renner parameterRenner parameter

pp = 2 = 2BB010010sin 2sin 2 == 4 4BB01001022/2r /2r

state constant 79BrCN+ 81BrCN+

2 p 0.020312(27) 0.020187(32) 2 p 0.018749(46) 0.018563(52) B010 0.1420111(23) 0.1412625(25) 2r 1488.4186(24) 1488.4050(30) 2 287.24(20)

79 = 0.18529(27) 81 = 0.18512(32)

: Renner parameter : Renner parameter

pp : : ––type doubling constant type doubling constant

BO2 (X 2) = 0.19

CO2+ (X 2u) = 0.190

Wave fuctions of Wave fuctions of 22 and and 22

sin 2 = 2/2 cos 2 = Aeff/2

sin2 : cos2 = 0.0040 : 0.9959

Large spin-orbit interaction !Large spin-orbit interaction !

SummarySummary 1. Near-infrared emission spectrum of the A 2+ - X 2 transition of the BrCN+ ion was observed by FT spectroscopy.

2. Rotational analysis of the four bands, A 2+ (000) - X 2 (000) ( =3/2 and 1/2 ) A 2+ (000) - 2 and A 2+ (000) - 2, was performed to determine the molecular constants.

3. The r0-structures of BrCN+ were obtained and geometrical difference between BrCN and BrCN+ was small.

4. Renner parameter was determined to be = 0.185, and the influence of the Renner-Teller effect on X 2 was turned out to be small due to the large spin-orbit interaction.

Conclusion Conclusion

2. Electronic transitions of linear triatomic radical cations were observed by FT spectroscopy.

1. Fourier Transform spectroscopy was combined with flowing afterglow technique to detect the polyatomic radical cation.

3. Accurate molecular constants were determined by the analysis of the observed vibronic bands.

5. The analysis of the Renner-Teller effect was accomplished.

4. Bond lengths and the harmonic frequencies of the ions were derived from the molecular constants.

Future worksFuture works

3. Vibrational transition of the ionic or radical species 3. Vibrational transition of the ionic or radical species

1. Detection of the radical species 1. Detection of the radical species

ArF excimer laser (193 nm) = 6.42 eVArF excimer laser (193 nm) = 6.42 eV

NN22*( *( A A 33++ ) = 6.22 eV, ) = 6.22 eV, =1.36 sec.=1.36 sec.

Fe(CO)5 + h (193 nm) FeCO

2. Detection of the triplet state of the molecule 2. Detection of the triplet state of the molecule

Hg* ( Hg* ( 33P P ) = 5.46 eV) = 5.46 eV

HCCH + Hg* ( 3P ) HCCH* + Hg ( 1S )

Emission or absorption spectrum of the transient species