MILLIMETER WAVE SPECTROSCOPY OF THE VINYL RADICAL (HDC=CH) GENERATED BY UV LASER PHOTOLYSIS IN A PULSED SUPERSONIC JET EXPANSION Masato HAYASHI, Kensuke HARADA, Keiichi TANAKA Department of Chemistry, Faculty of Sciences, Kyushu University

Vinyl radical H2CCH C2v(M) X2B2 DE0=0.543 cm-1 Proton Tunneling 0- 0- Double Minimum Potential C2v(M) X2B2 DE0=0.543 cm-1 H2CCH Proton Tunneling 0- 0- 1580 cm-1 0+ 0+ Hb Hb Hb Hb C C HDCCHもポテンシャル障壁の高さは同じであると考えられるがトンネル運動をするのかどうか興味がもたれる。 C C Ha Ha Proton Tunneling K. Tanaka, et al., J. Chem. Phys. 120, 3604 (2004)

Vinyl radical H2CCH H2CCD HDCCH C2v(M) X2B2 DE0=0.039 cm-1 Double Minimum Potential C2v(M) X2B2 H2CCH DE0=0.039 cm-1 Proton Tunneling 0- 0- 1520 cm-1 H2CCD HDCCH H2CCH DE0 0.039 0.543 1520 1580 h (cm-1) (Tunneling) 0+ 0+ Hb Hb Hb Hb C C HDCCHもポテンシャル障壁の高さは同じであると考えられるがトンネル運動をするのかどうか興味がもたれる。 D C C Tunneling K. Tanaka, et al., J. Chem. Phys. 120, 3604 (2004)

Vinyl radical H2CCH H2CCD HDCCH C2v(M) X2B2 Proton Tunneling DE0 0- 0- Double Minimum Potential C2v(M) X2B2 H2CCH Proton Tunneling DE0 0- 0- 1520 cm-1 0+ 0+ H2CCD (Tunneling) DE0 h (cm-1) D D Hb Hb H2CCD 0.039 1520 C C H2CCH 0.543 1580 C C H H HDCCH Tunneling ? K. Tanaka, et al., J. Chem. Phys. 120, 3604 (2004)

. . Vinyl radical cis , trans isomer HDCCH Cs X2A’ No tunneling effect ytrans ycis HDCCH Cs X2A’ cis , trans isomer No tunneling effect 0 trans 0 cis Dct large C D H . C D H . trans cis

. . Vinyl radical Proton tunneling Tunnel transition HDCCH Cs X2A’ Tunneling effect 0+ 0- Dct < = 1cm-1 very small D D H H C C C . . C H H trans cis

Setup supersonic jet 20 K pump UV laser 193 nm hn photolysis sample gas Setup vinyl chloride 1~3 % Ar : H2 = 3 : 1 10 ~ 15 atm MMW source: 109~163GHz supersonic jet 20 K pump UV laser 193 nm D H C C D H hn H C C H H Cl H C C D photolysis

Energy levels N HDCCH Ka = 0 Ka = 1 211 303 a-type transitions 212 KaKc Ka = 0 Ka = 1 211 303 a-type transitions 212 Observed transitions 110 111 202 101 000

Rotational transition 303 - 202 Obs. Calc. 163.52 163.54 [GHz]

303 - 202 Rotational transition Rotational transition Obs. Calc. 163.52 163.54 [GHz]

. Coupling scheme 303 202 J F1 F2 F C Hb D Ha ID N S Ib Ia J F1 F2 F Obs. C Hb D Ha ID N S Ib Ia J F1 F2 F ID = 1 1 2 Ia = . S = Ib =

. Molecular Constants of HDCCH Constant cis-HDCCH HDCCH [MHz] (B+C)/2 27311.392(17) DN 0.0745(10) εcc -33.51(18) aFa 37.1(12) Hb Ha Taaa 25.1(11) C C . aF b(H) 174.9(46) Db Taab(H) 5.71(63) cis-HDCCH aFb(D) 16.90(37) Taab(D) 1.45(38)

Rotational constants H H D H C C C C D H (B+C)/2 cis trans [MHz] Experimental value in good agreement 27311.392(17) CCSD(T)/cc-pVTZ 27312.225 27691.350 b H H D b H C C a C C a D H cis-HDCCH trans-HDCCH

Fermi contact interaction constant [MHz] cis-HDCCH aF(b1) = 184.7 aF(b2) = 111.0 ESR ( JACS. 94, 5950 (1972) ) C Hb1 Hb2 H H2CCH in Ar matrix Hb aF b(H) = 174.9 Ha C C D aFb(D) = 16.90 0.1535 aF(D) aF(H) = Experimental value 184.7 trans 111.0 cis 17.04 28.35 Estimated value from ESR cis [MHz] aF b(H) 174.9(46) aFb(D) 16.90(37) aF = mI I 8 3 p gs b Y(0) 2

. . Dct Observed Not observed Dct > 30 cm-1 = Estimated value of Dct cis-HDCCH Observed trans-HDCCH 0 trans Not observed 202-101 : 110650 MHz search : 110440~840 MHz 0 cis Dct cis-HDCCH S/N ~ 4 Temperature 20 K C D H . C D H . Dct > = 30 cm-1 trans cis Dct 41 cm-1 ~ CCSD(T)/cc-pVTZ

Dipole moment H H C C D 0.15 D 0.59 D cis-HDCCH Ka = 0 Ka = 1 a-axis a-type : b-type : cis-HDCCH b H H Ka = 0 Ka = 1 C C a 211 303 D 212 Dipole moment 110 111 202 a-axis 0.15 D 0.59 D b-axis 101 CCSD(T)/cc-pVTZ 000

Conclusions Future work a-type rotational transitions of cis-HDCCH were observed. The molecular constants of cis-HDCCH were determined. The energy difference Dct between cis- and trans-HDCCH is more than 30cm-1. Future work b-type rotational transitions of cis-HDCCH.

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Fermi contact interaction constant [MHz] HDCCH H Ha C C ・ D aFa(H) = 37.1 (12) H2CCH H Ha daF(b)　はaF(b1) － aF(b2)に対応します。気相中のビニルラジカルはﾄﾝﾈﾙ運動をしているため1,2とラベルすることは出来ませんが、Arマトリクス中ではﾄﾝﾈﾙ運動しないためこのようにtransとcisにラベルすることが出来ます。ESRの測定結果よりcis側のフェルミ相互作用は34G、trans側のフェルミ相互作用は68Gと報告されています。この結果よりaF(b)trans － aF(b)cisの値は47.6MHzと推定されます。実験値daF(b)は21.8MHｚとオーダーで一致しました。 C C ・ aFa = 37.019(12) H Millimeter wave spectroscopy( JCP. 120, 3604 (2004) )

スペクトル trans型　202 － 101 親分子 Obs. 110.62 110.64 [GHz]

スペクトル trans型　202 － 101 親分子 Obs. Calc. 110.62 110.64 [GHz]

Dct : 40 cm-1 Transition type cis-HDCCH trans-HDCCH Ka = 0 Ka = 1 a-type : b-type (cis-trans transitions) : b-type : cis-HDCCH trans-HDCCH Ka = 0 Ka = 1 Ka = 0 Ka = 1 111 110 212 211 000 101 202 303 211 303 212 110 111 202 101 Dct : 40 cm-1 000

y１ー y１＋ y0ー y0＋ D = 41cm-1

D b H C C a H trans-HDCCH a-axis 0.24 D 0.56 D b-axis

CCSD(T)/cc-pVTZ trans-isomer cis-isomer 32 cm-1 322 cm-1 331 cm-1 41 cm-1