+ millimeter-wave spectroscopy of ethylmercury hydride manuel goubet, roman a. motiyenko, laurent...
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+MILLIMETER-WAVE SPECTROSCOPY OF ETHYLMERCURY HYDRIDEManuel Goubet, Roman A. Motiyenko, Laurent MargulèsLaboratoire PhLAM, Université Lille 1Jean-Claude GuilleminsSciences Chimiques de Rennes - ENSCR
+Chemistry background
Synthesis of organomercury compounds: Guillemin, J.-C.; Bellec, N.; Kiz-Szetsi, S.; Nyulaszi, L.;
Veszpremi, T. Inorg. Chem. 1996, 35, 6586−6591. Craig, P. J.; Garraud, H.; Laurie, S. H.; Mennie, D.; Stojak, G.
H. J. Organomet. Chem. 1994, 468, 7−11.
Extensive spectroscopic and ab initio study of gaseous HgH2 and HgD2: Shayesteh, A.; Yu, S.; Bernath, P. F. J. Phys. Chem. A 2005,
109, 10280−10286.
+Ab initio structure of C2H5HgH
Method: MP2(full)
Basis sets: Hg - small core pseudo-
potential basis set: cc-pVTZ-PP, accounting for relativistic effects
C - cc-pCVTZ with extra core/valence functions
H - standard cc-pVTZ
Geometry optimization using « tight » convergence option
207.8 pm
161.5 pm
153.1 pm
113.5°
A = 29464.95 MHzB = 2817.15 MHzC = 2654.66 MHz
μa = 0.43 D; μb = 0.13 D
+The Lille fast scan spectrometer
BWOHV
PowerSupply
F/32+IF
Amplifier
Absorbing cell
DDS8.7 – 11.8
MHz
SR7270DSP Lock-
in amplifier
Bolometer
RS-232
SynthesizerAgilent E8257D
8 – 16.5 GHz
PLL,IF=8.7 –
11.8MHz
Amplifier
RS-2
32
Internal bus
Microcontroller ADuC 842
Ethernet
fast frequency switchingup to 20 μs/point
frequency range in this study: 120 – 180 GHz
Frequency synthesize
r Absorbing cell
Bolometer
to diffusion+
rotary pump
Sample at 250 K
At room temperature
+The spectrum
5.34 GHz ≈ B+C
f = (B+C)(J+1)
202Hg
201Hg
200Hg199Hg
198Hg204Hg
ν23 = 1 excited stateω= 199 cm-1
ab initio: B+C = 5.45 GHZ
201Hg I = 3/2
ν22 = 1 excited stateω= 233 cm-1
V3 = 1100 cm-1
CH3 top internal rotation ?
17 GHz spectrum recorded in ≈20 min (0.024 MHz frequency step)
+Calculation of nuclear quadrupole tensor
pseudo-potential should not be used
however high-level all electrons calculations of the electric field gradient for an atom like Hg might become unreasonably time consuming
the solution is to perform low level field gradient calculations (B1LYP/6-311G(df,p)) based on the geometry from high level calculations (see W.C. Bailey web-page at http://nqcc.wcbailey.net/)
F=? ??
?
+Calculation of nuclear quadrupole tensor Calculations have been made at the the HF, B1LYP and B3LYP levels
of theory
Basis sets: Hg - all electrons ANO-RCC C and H – cc-pVDZ, 6-311G(df,p), cc-pVTZ and ANO-RCC
For the consistency of the basis set over the molecule, the initial ANO basis was reduced to a double- or triple-zeta polarization according to the set used for H and C
The two-electrons integrals were calculated using the second order Douglas-Kroll-Hess (DKH) Hamiltonian to take into account the relativistic effect
The input geometry was the atomic Cartesian coordinates calculated at the MP2/cc-pVTZ-PP in the principal inertial axis orientation
+Calculation of nuclear quadrupole tensor: the results
The agreement is improving faster by increasing the level of the method than the quality of the basis set
If one has to compromise between accuracy and calculations time, the best choice would be a combination of a high level method and a small basis set
χaa
χbb
HF B1LYP B3LYPExperiment
cc-pVDZ
(126)
-1962
786
-1545
617
-1517
606
-1169.50(67
)
473.33(61)
6-311G(df,p)
(154)
-1956
784
-1532
612
-1503
600ANO-DZP
(180)
-1953
782
-1513
603
-1481
590cc-pVTZ
(237)
-1919
778
-1467
585
-1435
572ANO-TZP
(291)
-1942
778
-1415
562
-1376
546
63/2 – 61/257/2 – 55/2
61/2 – 59/259/2 – 57/2
+Calculation of nuclear quadrupole tensor: the results The angle between principal axis a and internuclear axis z
containing quadrupolar atom (Legon, A. C. Faraday Discuss. 1994, 97, 19):
χab can be estimated from the diagonal components in the assumption that the angular oscillation of the subunit containing the quadrupolar nucleus is two-dimensionally isotropic in the ab plane:
Estimation: χab = 644.78 MHz and αaz= 19.1°
From ab initio calculations: αaz = 19.6°
+Rotational spectroscopy: the results
202Hg 200Hg 199Hg 201Hg 198Hg 204Hg
A /MHz 29302.2001(35)
29464.946
29302.823(13) 29303.129(11) 29302.57(19) 29303.509(44) 29301.593(56)
B /MHz 2750.73634(10)
2817.149
2753.73409(19)
2755.25383(17)
2752.22888(73)
2756.79080(44)
2747.79563(50)
C /MHz 2593.295144(97)
2654.657
2595.96453(19)
2597.31756(17)
2594.62014(57)
2598.68407(43)
2590.67525(49)
ΔJ /kHz 1.349427(53)
1.372
1.352251(62) 1.353555(61) 1.35144(20) 1.355191(96) 1.34668(11)
ΔJK /kHz -28.73258(74)
-29.288
-28.76191(78) -28.77643(82) -28.7520(23) -28.7924(11) -28.7069(15)
ΔK /kHz 514.23(20)
496.021
513.07(94) 513.00(57) 514.23 516(16) 514.23
δJ /kHz 0.148784(10)
0.154
0.149193(44) 0.149477(45) 0.14952(16) 0.149911(88) 0.14848(12)
δK /kHz 6.1780(76)
6.127
6.241(28) 6.200(32) 6.64(10) 6.392(65) 6.270(62)
HKJ /Hz -2.0210(36) -2.0265(38) -2.0346(44) -1.996(11) -2.0342(56) -2.0291(99)
LKKJ /mHz 0.1296(43) 0.1334(48) 0.1467(60) - 0.1419(76) 0.143(16)
N lines 561 537 483 559 449 395
Jmax; Kmax 52; 26 51; 26 43; 24 34; 16 46; 25 34; 22
σ /MHz 0.024 0.023 0.019 0.041 0.027 0.026
+