Transcript Columbus13 HMP 2.ppt

OBSERVATION OF A MODERATE STRENGTH
INTERACTION OF HYDROGEN WITH A
COINAGE METAL HALIDE: THE ROTATIONAL
SPECTRUM AND STRUCTURE OF THE
para-H2-CuCl AND ortho-H2-CuCl COMPLEXES
Herbert M. Pickett, Daniel A. Obenchain
G.S. Grubbs II, Stewart E. Novick
Wesleyan University
Structure of the H2 - CuCl Complex
 Spectra shows clear effect of ortho-para
 Both B and C Rotational Constants in ortho states:
K0 (1 / C – 1 / B) = μ ( b 2 - c 2 ), μ = 0.5 amu,
K0 = 505379 MHz amu Å2
 For planar complex, c = 0 and b can be determined but
vibrational correction is probably required
 CI-37 or Cu-65 ortho spectra are needed to resolve
structures
 Ab initio calculations show agreement with experiments
b = 0.842 Å
r0 = 0.75095 Å
for free H2
Electric Quadrupole Interactions
 The Cu-63, Cu-65, Cl-35 and Cl-37 all have I=3/2
nuclei
• The orientation of the field gradient tensor will be
aligned with the CuCl bond due to masses
• Accordingly, χbb = χcc for both heavy nuclei
 As shown in the table below, both nuclei have a large
range of values. H2-CuCl is T shaped, while the Ar
and CO complexes are linear
CuCl
pH2-CuCl
oH2-CuCl
CO--CuCl
Ar--CuCl
X (Cu)
16.169
54.06
54.7
70.832
33.186
X (Cl)
-32.127
-24.3
-24.7
-21.474
-28.032
Parity and Hydrogen
 Must use wave function that has well-defined parity
 Early in the life of SPFIT there was only sequential
addition of spins
 While SPFIT could get a fit with lucky quanta, SPCAT
predicted double the number of lines
 Solution was to use symmetrized wave functions with
known parity (Itot =0,1)
 Check operator parity change is appropriate: bb-cc
operators connect K = 1 and K = -1
Treating the two coupled hydrogen nuclei as one
As is well-known, H2 can be in the para, Itot = 0, or ortho, Itot = 1, states
The spin-spin splitting in the para state is zero
For the ortho state the two nuclei can either be treated as
two interacting spin-1/2 nuclei or
as one combined nucleus with an effective spin of 1
the results are identical
Here are two var files for Pickett’s spcat
ortho test 4, single I = 1 nucleus
10 1000 5 0 0.1760E-11 0.10E+07 0.1E+01 1.0
'a' 3 1 0 10 0 1 1 1
0 1 1
10000 10000.
0.000
/ A
20000
2000.
0.000
/ B
30000
1000.
0.000
/ C
110010000
45.
0.000
/ 3/2 Daa
110040000
15.
0.000
/ 1/4 (Dbb - Dcc)
ortho test 5, two spins of I = ½
10 1000 5 0 0.1760E-11 0.10E+07 0.1E+01 1.0
'a' 22 1 0 10 0 1 1 1
0 1 1
10000 10000.
0.000
/ A
20000
2000. 0.000
/ B
30000
1000. 0.000
/ C
120010000
45. 0.000
/ 3/2Daa
120040000
15. 0.000
/ 1/4(Dbb - Dcc)
For both tests, Daa = 30 MHz, Dbb = 15 MHz, and Dcc = -45 MHz
one spin 1
the two cat files
two spin ½
The extra transitions in the file on the right are the para state transitions and are D independent