Rotational Spectra of Hydrogen-OCS van der Waals Complexes

Zhenhong Yu, Kelly Higgins, and William Klemperer

Department of Chemistry and Chemical Biology

Harvard University

Michael McCarthy and Patrick Thaddeus

Harvard-Smithsonian Center for Astrophysics

paraH2

orthoH2

orthoD2

paraD2

0

1

0

1

0 1

1 3

0 and 2 1 and 5

1 3

j I T

Observed a-type transitions of hydrogen-OCS complexes at K-1 = 0

pH2-OCS oH2-OCS HD-OCS oD2-OCS pD2-OCS

1-0 10595.586 10218.271 10024.997 9517.559 9289.155

2-1 21108.051 20385.664 19860.567 18728.252 18345.878

3-2 31455.677 30451.299 29332.064 27378.219 26966.614

The spectroscopic constants of hydrogen(j=0)-OCS complexes

pH2-OCS oD2-OCSHD-OCS

A

B

C

J

JK

K

J

K

22416.75(103) 15971.889(162) 12829.367(75)

5995.977(308) 5849.626(116) 5671.594(74)

4599.888(297) 4175.804(109) 3846.491(67)

0.06919(252) 0.10653(184) 0.13153(168)

5.2597(148) 2.7398(109) 1.1684(97)

24.17(105) 6.460(173) 3.491(85)

0.017581(135) 0.030666(103) 0.046989(155)

4.541(150) 2.529(56) 1.256(34)

CO S

H

H

R

a

b

θ

β

j

pH2-OCS

oH2-OCS

HD-OCS

oD2-OCS

pD2-OCS

10595.5 10595.6 10595.7

Frequency(MHz)

10218.2 10218.3 10218.4

10024.9 10025.0 10025.1

9517.4 9517.5 9517.6 9517.7

9289.0 9289.1 9289.2 9289.3

H = HSS + Heq for oD2-OCS

d0 = 3 and eqQ0 = 223 kHz for oD2

I = 0 I = 2

F = 1 (20.0) 0eqQ

0.153eqQ

F = 1 (20.0) -0.175eqQ

-0.328eqQ

F = 3 (46.7) -0.05eqQ

F = 2 (33.3) 0.175eqQ

IJFHJFI ' is nonzeroThe off-diagonal matrix element

Nuclear hyperfine coupling constants of hydrogen-OCS complexes

da = d0<P2(cos)> or eqQa = eqQ0<P2(cos)>

oH2-OCS HD-OCS oD2-OCSpD2-OCS

da

eqQa

<P2(cos)>

<P2(cos)>

21.2(2)

0.368(4)

0.032(4)

16(2)

0.071(9)

0.071(9)

30(2)

0.129(8)

0.129(8)

8.4(2)

0.333(8)

0.067(8)

j = 1 j = 0

Structural parameters of the hydrogen(j = 0)-OCS complexes

R(Å)

pH2-OCS

HD-OCS

oD2-OCS

He-OCS

Ne-OCS

Ar-OCS

N2-OCS

(degree)

3.72

3.64

3.59

3.82

3.53

3.70

3.98

109.7

108.7

108.1

113.9

109.6

107.0

110.3

Summary

• The ground state of hydrogen-OCS complex has T-shaped geometry.

• The internal rotation of hydrogen molecule is decoupled from the molecular axis, leaving the end-over-end rotation of the complex well conserved.

• Nuclear hyperfine structure indicates that the internal rotation of hydrogen molecule is slightly hindered.

• The nuclear spin states I = 0 and 2 of orthoD2-OCS are strongly coupled through the overall rotation of the complex.