Nuclear Spin Conversion Interaction and orthopara Conversion Rates
- Slides: 20
Nuclear Spin Conversion Interaction and ortho-para Conversion Rates in the Vinyl Radical Keiichi TANAKA, M. Hayashi, M. Ohtsuki, K. Harada, T. Tanaka Department of Chemistry, Kyushu University Fukuoka, Japan (Columbus. 2010) Ohio June 21,
Nuclear Spin Conversion Interaction Ortho – Para Conversion Rates in the Vinyl Radical H H 2 CCD, D 2 CCD H C Para How fast does it occur? A MagicAwith Vinyl . C Keiichi Tanaka, Kyushu University Ortho D
Para- H 2 Nuclear Spin Conversion Para Ortho, + 4 + p - - para-H 2 ortho-H 2 3 H H 2 1 0 H (I=0, J=even) H (I=1, J=odd) o + p -+ 1 S + g Para and Ortho never interact each other: Poly-atomic Molecules: They are different. Spin-Spin species Hyperfine Magnetic Interaction: Spin-Rotation, o p
Collision Induced Nuclear Spin Conversion of Ethylene H 2 CCH 2 : B 2 u B 3 u Collision induced N. S. Conversion t C 2 H 4 t = 30 min -2. 4 % by LID P = 1. 44 Torr K. Takagi et. al. , . Science (2005) (min) 30 CH 3 F 76 H 2 CO 87 with P ~ 1 Torr 1/t ∞ P
Collision Induced NSI Conversion para ortho <O|H'|P> DE Collisions Accidental degeneracy DE Ortho-Para Interaction <O|H'|P> y' = yortho + a ypara a = <O|H'|P>/ DE Channel Conversion Rate k(O→P) = 2 krot <o| H |p>i DEi 2 : S exp(-DEi/k. T)/Q krot : Collision : 108 sec-1 Torr-1
Nuclear Spin Conversion Interaction B ~J H 1 H 2 DI = ± 1, ortho-para interaction IH = 1, 0 Off –diagonal nuclear spin-rotation : C O ortho, para Cab. J (I 1 - I 2) ½(Cab+Cba) = 21. 0 k. Hz Rotation off-axis Two protons are no more identical B~S H 1 IH = 1, 0 C H 2 C S = 1/2 D Fermi Contact Int. : da. F(b) S ( I 1 - I 2 ) <O |H’| p> = da. F(b), tunneling DI = 0 da. F(b) = 69. 58(48) MHz open shell molecule ; DI = ± 1, interaction is much larger Vinyl
Proton Tunneling of the Vinyl Radical H DEC 0 h D C Exprimental MMW q 0 - H + ab initio ( CCSD(T)) 0 Structure: J. H. Wang et al. Chem. Phys. (1996) H H C C H H H C (cm-1) DE 0 h H 2 CCH 0. 542 8 1580 H 2 CCD 0. 039 4 1520 D 2 CCD 0. 025 7 1549 CCSD(T) 1653 cm-1 C H ~ B. O. Approx.
H 2 CCD Tunneling-rotation Transitions - + ortho 0 para Ib = 1 303 211 212 + 110 111 + 101 - 000 Ka = 0 + + - R(0) Ib = 0 + 211 212 - + - 110 111 R(0) tunneling-rotation transitions 1 para Ib = 1 Ib = 0 - 202 0 Ka = 0 303 + 202 - 101 + 000 1 DE 0 = 1164 MHz
ortho-para interaction of H 2 CCD Tunneling-rotation transition, R(0) - 0 + ~2. 4 MHz 0 ortho + 0 - 0 236760 70 ~2. 4 MHz 810 20 para 234340 50 480 90 MHz
DIb = ± 1, ortho-para interaction H 2 CCD - + 0 ortho Ib = 1 303 - ortho Ib = 0 Ib = 1 + dn =1. 87 MHz 110 111 a 2 = 0. 1 % 202 211 212 para + - 000 Ka = 0 + 1 Ib = 0 211 212 - + - 110 111 1/2 da. F S DI - para + + 101 0 dn =0. 56 MHz Ka = 0 303 + 202 - 101 + 000 1 DE 0 = 1164 MHz
Ortho-Para Mixing Interaction H 2 CCH H 2 CCD D 2 CCD 68. 06 10. 65 68. 06 MHz da. F(b) DE 0 1 187 772 16 272 MHz Dn 0. 94 0. 13 0. 075 MHz a 2 0. 092 0. 012 0. 00043 Para DE 0 Ortho Dn da. F(b) shift a 2: mixing coefficient %
Ortho-para Conversion Rate H 2 CO para ortho Cab = 10 k. Hz 173, 15 Kp→o = para H 2 CCD para (0 -) ortho (0+) da. F = 68. 06 MHz 182, 17 202 3. 9 GHz -1 6. 8× 10 -5 s-1xTorr 109 202 101 2 <o| H |p> 000 Kp→o = 2 krot 1. 2 GHz DE times faster Kp→o = 1. 2× 105 s-1 Torr-1 krot : 108 sec-1 Torr-1 : collision Collision 101 000 para P = 1 Torr Collision P = 1 Torr t = 8. 3 ms t = 245 min ortho 303 ortho
Ortho-Para Converstion Rates in Vinyl I’→ I” H 2 CCD D 2 CCD H 2 CCH k(0→ 1) k(1→ 0) k(1→ 2) k(2→ 1) 1. 2 x 105 4. 1 x 104 2. 0 x 104 6. 8 x 103 4. 2 x 103 2. 5 x 103 6. 5 x 102 s-1 torr-1 2. 2 x 102 “ “ “ t(0→ 1) t(1→ 0) t(1→ 2) t(2→ 1) 8. 3 ms 24. 4 ms 50. 0 147 238 400 ms ms 1. 54 4. 54 ms ms (P = 1 Torr)
ortho-para Relaxation: Radiative H 2 CCD + ortho 0 303 Trot ~ 3 K 0 - + + 211 212 + - 110 111 212 + 110 111 + - t = ~0. 5 days t = ~125 days 101 - 000 Ka = 0 + 0 - + 0 - 202 para 1 Tn. s. ~ Trot Ka = 0 - 303 + 202 - 101 + 000 1 DT = 0. 8 K
Conclusions Ortho-Para Mixing Interaction da. F(b) 68. 06(53) MHz 10. 63(93) “ a 2 0. 1% H 2 CCD 0. 01 % D 2 CCD Ortho-Para Conversion Rates (Collision Induced) t (0→ 1) 8. 3 ms t (1→ 0) 24. 4 ms H 2 CCD t (0→ 1) 50 ms t (1→ 0) 147 ms D 2 CCD (P = 1 Torr ) NSI Conversion for Radicals is more than 106 times faster than that for the closed shell molecules.
H H 3+ H H Ortho I = 3/2 Para I = 1/2
Radiative Relaxation Process of H 3+ J H H H 3+ R(3, 3) 2 R(1, 1) (3, 3) H Centrifugal + Galactic Center H 3 1 DK = + 3 K 500 K (2, 2) (1, 1) Distortion Tn. s. » Trot Ortho Para 3 μ + Ortho 0 1 Ortho 2 3 Para Oka, Epp, APJ (2004)
H 2 CCD H 2 CCH H 1 H 2 H 1 C 2 v(M) H D Large tunneling splitting : Small tunneling splitting : DE 0= 0. 039 cm-1 DE 0= 0. 547 cm-1 DIb = Ib 1 - Ib 2, da. F = 69. 6 MHz Ib = Ib 1+ Ib 2 = 0, 1 ortho-para interaction ortho-, para-vinyl fast ortho-para conversion
Molecular symmetry : C 2 v(M), G 4 (E, E*, (12)*) Inversion E* : E*Yt = ±Yt Permutation (12) : (12)Yt = ±Yt , + Boson Reserved Yt Broken ! - Fermion = Ye. Yv. Yr Parity : ± X 1 (D) (H) H(D) C C X 2 Yns (12)Ye. Yv. Yr = ±Ye. Yv. Yr a, s ; (12)Yns = ±Yns a, s ; ± . C 2 v(M) ± ortho, para is the symmetry only for Yns
Fin Thank you for your Attention !! A MagicAwith Vinyl A Magic with Vinyl; Keiichi Tanaka, Kyushu University
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