Millimeter-wave Spectroscopy of the Tunneling-rotation Transitions of the D2CCD radical

M. Ohtsuki, M. Hayashi, K. Harada, K. Tanaka Department of Chemistry, Faculty of Sciences, Kyushu University

International Symposium on Molecular Spectroscopy 63rd –Meeting

The Ohio State University

Introduction

C

C

H

H H

C

CH H

Hα

H2CCH

DE0 = 16 .271 GHz

h = 1580 cm-1

J. Chem. Phys. 120, 3604 (2004)

Previous Work

b

H2CCDDE0 = 1 .186 GHz h = 1520 cm-1

D DD2CCDDE0 = ? h = ?

Present Work

DDDD

DE

0 h

DE0:Tunneling splitting h:Potential Barrier height

0+

0-

h < 1800 cm-1

000

101

202

303

211

212

110111

000

101

202

303

211

212

110111

Ka = 0 Ka = 1 Ka = 0Ka = 1

0+

0-N KaKc

a-type transition E. Kim, et al., J.C.P 116, 10713(2002)

DE0

C C

Db

Db

Daa

bIntroduction-Pure rotatonal Transition- ma = -0.1611 D

para paraortho ortho

b-type transition

R(0)

Q(1)R(1)

DE0

C C

Db

Db

Daa

b

000

101

202

303

211

212

110111

000

101

202

303

211212

110111

Ka = 0 Ka = 1 Ka = 0 Ka = 10+ 0-

Introduction-Tunneling-rotation Transition-

mb = -0.5863 D

para paraortho ortho

UV laser193 nm

Sample(Ar : 7 atm + H2: 3 atm)

+D2CCDCl : 0.2 atm

C CD

D

D

Cl

PhotolysisArF

Experimental setup

Trot=20 KC C

D

D

D

D

D D

C C

Millimeter-wave100 ~ 200 GHz

White-type multi-reflection cell (10 round trips)

Obs.

143.5 143.55143.45Frequency(MHz)

Observed Tunneling-rotation Spectra R(0)(0-←0+)

J :0.5 ←0.5 J :1.5 ←0.5Para:Ib=1

Calc.

N

S

F

F1J

Ib Ia

N : Rotation

S : Electron spin

I : Nuclear spin

Coupling of Angular Momenta

(0-)111-(0+)000

Ia= 1C

DC

D

D

S = 0.5

I b= 0,1,2

SIb Ia

Para : Ib=1 Ortho : Ib=0,2

Ortho:I b = 0,2

Observed Tunneling-rotation Spectra R(0)(0+←0-)

Obs.

J :0.5 ←0.5 J :1.5 ←0.5

142.00141.90 (GHz) 141.95

Calc. Ib = 2

Calc. Ib = 0

Frequency (GHz)

Q(1)

R(0)R(1)

Q(2)

120100 160 180

2DE0

140 GHz

(0+←0-)(0-←0+)

1.54GHz

140

Q(3)

Observed Tunneling-rotation Spectra 0-0+

DE

0

6:3

6:3

ortho

ortho

200

para

para

Constants (MHz) (average) FTMW (MHz) (average)

DE0 771.858 (24) -

A 122 560.835 (50) -

B 24 264.477 (38) (B + C)/2 = 22 220.523 32(25)C 20 175.989 (38)

eaa 120.666 (24) -

(ebb+ecc)/2 -24.11 (33) -24.095 1(19)

aF (a) 5.872 (11) 5.874 5(27)

Taa(a) 4.130 (14) 4.123 5(42)

Tbb(a) 0.97 (11) -

aF (b) 21.617 (32) 21.608 7(111)

Taa(b) 1.302 9 (80) 1.293 5(23)

Tbb(b) - 0.274 (56) -

d aF (b) 8.5 (13) -

s = 160.8kHzData:93 ( MMW(61) + FTMW(32))

Molecular Constants

Off-diagonal Fermi interaction constant

average : (0+ + 0-) / 2

Potential Barrier Height

C

C

D

D D

C

CD D

D

qmin = 43.4°

DE0 (MHz) h (cm-1)

D2CCD 　 771.858 (24) 1549

H2CCD 1 186.820 (21) 1520

H2CCH 16 271.842 9(59) 1580

V(q) = -V2q 2 + V4q 4

h =V2

2

4V4*qmin is fixed (CCSD(T)/TZ2P) (Chem. Phys.206, 43 (1996))DE

0 h

q

0+

0-

qmin

Ortho-Para Interaction

000

101

110

111

000

101

110

111

Ka = 0 Ka = 1 Ka = 0Ka = 10+ 0-

para ortho para ortho

R(0)Tunneling-rotation Transitions (DIb = 0)

Ortho-Para Interaction (DIb = 1)

Ortho (Ib = 0, 2)Para ( Ib = 1)

DE0= 771MHz

dn = 0.094 MHz

dn = -0.094 MHz

++

+

+

-

-

-

-

12 daF S DIbHF

( )b =

ortho-para interaction

aF( )b = (aF

( 1)b + aF( 2)b )/2

daF( )b = aF

( 1)b - aF( 2)b

DIb = I 1b - I 2b

(MHz) D2CCD H2CCD

daF( ) b 8.5 (13) 67.14 (67)

DE0 771.858 (24) 1 186.820 (21)

dn (interaction) 0.094 0.94

a2(mixing ratio) 0.012 % 0.080 %

Ib = I 1b + I 2b

Ortho-Para Interaction (DIb = 1)

dn

dn

0+ (111)

0- (111)

HF(b) = aF

( 1b ) S I 1b + aF( 2b ) S I 2b

= aF(b) S Ib + (daF

(b)S DIb)/2

○ 　 Tunneling-rotation Transition of D2CCD radical was observed and assigned.

○ 　 Tunneling splitting (DE0) was determined to be 771.858 (24) MHz.

○ 　 Potential barrier height(h) was estimated to be 　 1549 cm-1 .

Conclusions

○ 　 Off-diagonal Fermi interaction term,daF( ) b ,

was determined to be 8.5 (13) MHz at D2CCD.

Thank you for your attention!!