Is the Equilibrium Structure of BeOH Linear or Bent? Kyle Mascaritolo Dr. Michael Heaven.
Transcript of Is the Equilibrium Structure of BeOH Linear or Bent? Kyle Mascaritolo Dr. Michael Heaven.
Significance of ResearchMonohydroxides of Mg, Ca, Sr and Ba have all been studied experimentally and computationally
For the Ground State: Linear: CaOH, SrOH, BaOH [1-3]
– Ionic Bonding M+X-
Quasilinear: MgOH [4]
– Some Covalency, barrier to linearity < 2 cm-1
BeOH calculated to be bent, but little experimental data 1. D.O. Harris, J. Mol. Spectrosc. 97, 73 1983.
2. D.O. Harris, J. Mol. Spectrosc. 97, 37 1983.3. P.F. Bernath, J. Chem. Phys. 84, 698 1986.4. Y. Ni, Ph.D. thesis, Uni. California, Santa Barbara, 1986.
Past Computational Findings
Several high-level ab initio calculations for BeOH predict: [1-3]
– Equilibrium BeOH ranging ∠134° - 152°
– Barrier to linearity up to 136 cm-1,
but as low as 50 cm-1
– Near Prolate Top: B0 ≈ 1.29 cm-1
– A significant contribution of covalency to the Be-O bonding
1. Theodorakopoulos, Petsalakis, and Hamilton J. Chem. Phys. 111, 23 1999.2. Koput and Peterson J. Phys. Chem. A 107, 2003.3. Palke and Kirtman Chem. Phys. Lett. 117, 5 1985.
Barrier to Linearity: 136 cm-1
∠BeOH = 140.9°
Possibly quasilinear in ground state
Method: RCCSD(T) cc-pV5Z
Equilibrium Bending Potential with vl2 Bending Energy Levels
Koput and Peterson J. Phys. Chem. A 107, 2003.
-8000
-7000
-6000
-5000
-4000
-3000
-2000
-1000
100 110 120 130 140 150 160 170 180
Re
lativ
e E
ne
rgy
/cm
-1
Angle / degrees
X2A'
12A'
12A"
-3500
-3000
-2500
-2000
-1500
-1000
1.25 1.3 1.35 1.4 1.45 1.5 1.55 1.6
Re
lativ
e e
ne
rgy
/cm
-1
R(BeO) /A
12A"
CASSCF/MRCI/ aug-cc-pVTZ
12A” State Calculations
R(BeO)=1.457, R(OH)=0.954, q=127.6; B0=1.228 cm-1
Calculations done by Dr. Michael Heaven
Excited states shifted down for comparison
Renner-Teller
Past Experimental Results
Low resolution gas phase electronic spectroscopy
– 300 – 330nm(30300 – 33330 cm-1)– Was not analyzed in detail
A. Antic-Jovanovic, V. Bojovic, D. Pesic, Spectrosc. Lett. 21, 8 1988.
Experimental Setup: Laser Induced Fluorescence and 1 + 1’ Resonance Enhanced Multiphoton Ionization Spectroscopies
LIF and REMPI Excitation Photon: Doubled output of 2nd Harmonic Nd:YAG pumped dye laser (Quanta Ray PDL1)REMPI Ionization Photon: 248nm from KrF Excimer (COMPexPro 102)Ablation Photon: Fundamental of Nd:YAG (Continuum Mini-Lite II)
Base Pressure: 1x10-7 Torr
Base Pressure: 1x10-9 Torr
Smalley Laser Ablation
1 + 1’ REMPI Survey
30400 30800 31200 31600 32000 32400 32800
400
500
600
Wavenumbers (cm-1)
BeOH
BeOD
752 cm-1708 cm-1
579 cm-1561 cm-1517 cm-1
0000
Transitions from 0000
0200
?
0110
00000110 03100200
Laser Induced Fluorescence
31000 31250 31500 31750 32000 32250 32500
0
200
400
600
800
BeOD
BeOH
Wavenumber (cm-1)
30850 30900 30950 31000 31050
0
100
200
300
400
500
600
700
BeOD
BeOH
Wavenumber (cm-1)
LIF of Current Lowest Rovibronic Transition
K’=0 ← K”=1
K’=2 ← K”=1
K’=1 ← K”=0
K’=1 ← K”=0
K’=0 ← K”=1BeOH
Perpendicular transitions
Energy Level Diagram for Prolate Top∆K = ±1 ∆J = 0,±1E = BJ(J+1)+(A-B)K2
J=01
2
3
J=0
1
2
3
1
2
3
1
2
3
2
3
2
3
K=0 K=1 K=2
v”
v'
≈160 cm-1 BeOH≈100 cm-1 BeOD
T = 15KkT ≈ 11 cm-1
≈40 cm-1 BeOH≈26 cm-1 BeOD
BeOD
30860 30880 30900 30920 30940 30960 30980 31000 31020 31040 31060Wavenumber/cm-1
0.1
0.2Nor
mal
ized
Inte
nsity
/ cm
-1
Obs.
Calc.
BeOH
” = 1.2150(58) cm-1
’ = 1.2044(49) cm-1
T = 15K
K’=0 ← K”=1 K’=1 ← K”=0 K’=2 ← K”=1
BeOD
30860 30880 30900 30920 30940 30960 30980 31000 31020 31040 31060Wavenumber/cm-1
0.1
0.2Nor
mal
ized
Inte
nsity
/ cm
-1
Obs.
Calc.
BeOH
” = 1.2150(58) cm-1
’ = 1.2044(49) cm-1
T = 15K
K’=0 ← K”=1 K’=1 ← K”=0 K’=2 ← K”=1
K’ = 2 ← K”=1?
31025 31030 31035 31040 31045 31050 31055 31060 31065Wavenumber/cm-1
0.005
0.010
Norm
alize
d In
tens
ity /
cm-1
Q
R(0) R(1) R(2)P(1)P(2)P(3)P(4)
R(1)R(2)
P(3)P(4)
Q
Be2O?
BeOD
30860 30880 30900 30920 30940 30960 30980 31000 31020 31040 31060Wavenumber/cm-1
0.1
0.2Nor
mal
ized
Inte
nsity
/ cm
-1
Obs.
Calc.
BeOH
A”-A' ≈ 20 cm-1
” = 1.2150(58) cm-1
’ = 1.2044(49) cm-1
T = 15K
K’=0 ← K”=1 K’=1 ← K”=0 K’=2 ← K”=1
30850 30900 30950 31000 31050
0
100
200
300
400
500
600
700
BeOD
BeOH
Wavenumber (cm-1)
LIF of Current Lowest Rovibronic Transition
K’=0 ← K”=1
K’=2 ← K”=1
K’=1 ← K”=0
K’=1 ← K”=0
K’=0 ← K”=1BeOH
30965 30970 30975 30980 30985 30990 30995 31000 31005 31010 31015Wavenumber/cm-1
0.1
0.2
Norm
aliz
ed Inte
nsity / c
m-1
30850 30855 30860 30865 30870 30875 30880 30885 30890Wavenumber/cm-1
50
100
/1e-
6N
orm
aliz
ed In
tens
ity /
cm-1
BeOH
A”-A’ ≈ 40 cm-1
” = 1.247(14) cm-1
= 1.241(12) cm-1
T = 15K
BeOD
K’=1 ← K”=0
K’=0 ← K”=1
Simulation done with PGOPHER
1 + 1’ REMPI Survey
30400 30800 31200 31600 32000 32400 32800
400
500
600
Wavenumbers (cm-1)
BeOH
BeOD
If we have K’=0 ← K”=1,then why no K’=2 ← K”=1?
BeOH
BeOD
Constants”
0000 1.246(14) 1.2453(86)
0110 1.2485(84) 1.2461(88)
0000 1.280(15) 1.224(13)
”
0000 1.1892(86) 1.1860(63)
0110 1.134(11) 1.1333(96)
0200 1.0934(80) 1.0922(87)
0310 1.106(27) 1.100(21)
Future Work
• Explore to higher and lower energy• Make spectra “hot” by increasing ablation
laser power to populate K” = 1,2,…• PFI-ZEKE to get geometry of cation• Find ionization potential
Acknowledgements
LabmatesIvan AntonovKeith FreelJoshua BartlettMichelle SullivanJiande Han
Past WorkJeremy Merritt
Quasilinear MgOH/OD
rx/re = 1.38 for MgOH stated by Murad
rx > 2re to be ionic (rx = 2.5 Å, re = 1.8 Å)
rx
E. Murad, J. Chem. Phys. 75 1983.
Ground State Bending Potential of BeOH at Different RBe-O Bond Lengths
RBe-O ≤ 2.4 Bohr → Linear
RBe-O ≥ 2.4 Bohr → Bent
Calculated Equilibrium:RBe-O = 2.6 Bohr (1.3775 Å) at BeOH = 142.5°∠
Barrier to Linearity = 50 cm-1
Method: MRD-CITheodorakopoulos, Petsalakis, and Hamilton J. Chem. Phys. 111, 23 1999.
Past Experimental Results
• Ar Matrix-isolated ESR spectroscopy [1]
– Assumed ionic– Small evidence of bent
structure taken as false signal
• Low resolution gas phase electronic spectroscopy [2]
– 300 – 330nm(30300 – 33330 cm-1)– Was not analyzed in detail 1. J.M. Brom, Jr. and W. Weltner, Jr. J. Chem. Phys. 64, 9 1976.
2. A. Antic-Jovanovic, V. Bojovic, D. Pesic, Spectrosc. Lett. 21, 8 1988.
29360 29365 29370 29375 29380 29385 29390 29395 29400
Be18OH
Be16OH
Be
OH
+ io
n C
urr
en
t
Enegry /cm-1
31 74 0 31 74 5 31 75 0 31 75 5 31 76 0 31 76 5 31 77 0Wa v e nu mb er/c m-1
0 .0 5
0 .1 0
No
rma
lize
d In
ten
sity
/ cm
-1
LIF of 2A”- X2A’: Be16OH & Be18OH
Simulation with B’=1.22, B”=1.28 cm-1 T=20 K
obs.
calc.
Effects of Isotopic Substitution
Work done by Jeremy Merritt: M. Heaven
Doesn’t show asymmetric splittings. Deuteration needed to characterize bending motion.
30860 30870 30880 30890 30900 30910 30920 30930 30940 30950Wavenumber/cm-1
0.1
0.2
Norm
alize
d In
tens
ity /
cm-1
BeOD
Without High Energy SatelliteA” = 26.85(50) cm-1
” = 1.1892(86) cm-1
A’ = 46.399(53) cm-1
’ = 1.1860(63) cm-1
T = 15K
With High Energy SatelliteA” = 26.885(48) cm-1
” = 1.2150(58) cm-1
A’ = 46.465(16) cm-1
’ = 1.2044(49) cm-1
T = 15K
Laser Induced Fluorescence
31000 31250 31500 31750 32000 32250 32500
0
200
400
600
800
BeOD
BeOH
Wavenumber (cm-1)
BeOD
31975 32000 32025 32050 32075 32100
100
200
300
400
BeOD
BeOH
Wavenumber (cm-1)
00000110
v2 predicted at 52.9 cm-1
Koput and Peterson J. Phys. Chem. A 107, 2003.
30965 30970 30975 30980 30985 30990 30995 31000 31005 31010 31015Wavenumber/cm-1
0.1
0.2
Norm
aliz
ed Inte
nsity / c
m-1
30850 30855 30860 30865 30870 30875 30880 30885 30890Wavenumber/cm-1
50
100
/1e-
6N
orm
aliz
ed In
tens
ity /
cm-1
BeOH
A” = 79.455(84) cm-1
” = 1.247(14) cm-1
A’ = 46.241(89) cm-1
’ = 1.241(12) cm-1
T = 15K
BeOD
K’=1 ← K”=0
K’=0 ← K”=1
Simulation done with PGOPHER
∠BeOH” = 167.8°∠BeOH’ = 158.6°
BeOD
30860 30880 30900 30920 30940 30960 30980 31000 31020 31040 31060Wavenumber/cm-1
0.1
0.2Nor
mal
ized
Inte
nsity
/ cm
-1
Obs.
Calc.
BeOH
A” = 26.885(48) cm-1
” = 1.2150(58) cm-1
A’ = 46.465(16) cm-1
’ = 1.2044(49) cm-1
T = 15K
K’=0 ← K”=1 K’=1 ← K”=0 K’=2 ← K”=1
∠BeOH” = 141.2°∠BeOH” = 158.7°
BeOH
BeOD
ConstantsA” ” A’
0000 85.630(50) 1.246(14) 40.168(85) 1.2453(86)
0110 82.3764(28) 1.2485(84) 47.610(68) 1.2461(88)
0000 73.289(23) 1.280(15) 59.069(89) 1.224(13)
A” ” A’
0000 26.85(50) 1.1892(86) 46.399(53) 1.1860(63)
0110 26.978(71) 1.134(11) 47.353(70) 1.1333(96)
0200 26.8146(45) 1.0934(80) 49.736(48) 1.0922(87)
0310 21.21(14) 1.106(27) 58.90(13) 1.100(21)