High-resolution Fourier transform emission spectroscopy of the A 2  + – X 2  transition of the BrCN + ion. June 20, 2005, Ohio state Univ. Yoshihiro Nakashima (a), Tomoki Ogawa, Maki Matsuo, and Keiichi Tanaka Department of Chemistry, Faculty of Science, Kyushu University, Fukuoka, Japan (a) : Ozone Layer Research Project, National Institute for Environmental Studies (NIES), National Institute for Environmental Studies (NIES), Ibaraki, Japan Ibaraki, Japan

A =  1477 cm cm -1 Introduction Influence of the large spin-orbit interaction large spin-orbit interaction on the Renner-Teller effect  2 = (20) cm cm -1 BrCN + ion Renner-Teller effect Renner-Teller effect Large spin-orbit interaction Large spin-orbit interaction X 2  Electronic ground state : X 2 

Previous works 2. M. A. Hanratty et al. B 2  3/2  X 2  3/2 LIF spectra of the B 2  3/2  X 2  3/2 transition 4. C. Salud et al. Infrared diode laser spectroscopy of the 1 (CN str.) fundamental band 1 (CN str.) fundamental band X 2  3/2 of the X 2  3/2  state 1. J.Fulara et al. Low-resolution emission spectra B 2  3/2  X 2  3/2 of the B 2  3/2  X 2  3/2 and A 2    X 2  A 2    X 2  transitions A 2  + X 2   B 2   0 13,700 19,230 cm -1 (001) (002) (012) (100) 3. M. Rosslein et al. LIF spectra of the B 2  3/2  X 2  3/2 transition to determine the r s -structure r s -structure of BrCN +

Experimental He (1.0 Torr) BrCN (2-3 mTorr) resolution : 0.02 cm -1 spectral region : – cm -1 accumulation time : 40 hrs. Penning ionization He*(2 3 S) + BrCN BrCN + + He(1 1 S) (I.P.=12.08 eV)

Observed spectrum ( A 2  + - X 2   ) (010)-(000) (010)-(010) (000)-(000) (001)-(011) (010)-(001) (100)-(100) (001)-(001)  =3/2 (000)-(010) A 2  + -  2  (000)-(100)  =1/2 (000)-(000) (010)-(010) (001)-(001) (000)-(010) A 2  + -  2 

A 2  + (000) - X 2  3/2 (000) transition P1P1 R 21 P 21 + Q 1 R 1 + Q 21

A 2  + (000) - X 2  3/2 (000) transition P 1 branch 79 BrCN + J’’=35.5J’’= BrCN + J’’=35.5J’’=39.5

Molecular constants (unit : cm -1 ) state constant  =3/2  =1/2 D.L. (  =3/2) A 2  +  (13) (46) B (51) 10 7 D 0.346(16)  (37) X 2   B  (47) (62) (41) 10 7 D 0.307(15) 0.347(11) 0.158(23)  q + p/2  (11) eff A 2  + (000) – X 2   (000) transition of 79 BrCN + 79 B 000 = (32) cm B 000 = (41) cm -1 Rotational constant B 000 B 3/2 = B 000 ( 1 + B 000 /A eff ) B 1/2 = B 000 ( 1  B 000 /A eff ) eff A eff = 1/2 – 3/2 79 A eff =  (48) cm A eff =  (60) cm -1 Effective spin-orbit interaction constant A eff low resolution emission spectroscopy A =  1477 cm -1

r 0 -structure I =  m k z k 2 0 =  m k z k  I = z Br 2  m Br  m k  m Br +  m k BrCN × z Br zCzC zNzN G species electronic state r BrC r CN BrCN X 1  BrCN + X 2  1.788(54) 1.103(78) 1.745(7) a 1.195(8) a A 2  (61) 1.064(90) unit : A a : The r s -structure determined by Rosslein et al.

Main electronic configuration (3  ) 2 (1  ) 4 (4  ) 2 (2  ) 4 : BrCN (X 1  + ) (3  ) 2 (1  ) 4 (4  ) 2 (2  ) 3 : BrCN + (X 2  ) (3  ) 2 (1  ) 4 (4  ) 1 (2  ) 4 : BrCN + (A 2  + ) 4p (Br) –  (CN) p z (N) (non-bonding) Geometrical change is small ! p (Br) (non-bonding)

A 2  + -  2  transition P2P2 R2R2 P 12 R 12

Molecular constants (unit : cm -1 ) state constant  2   2  A 2  + (000) (12) (21) B a 10 7 D a  a X 2  (010)  B (19) (25) 10 7 D (60) (58) p  (27)  (46) A 2  + (000) – X 2   (010) transition of 79 BrCN + Rotational constant B B 010 = (23) cm B 010 = (25) cm -1 B  = B 010  [ (B 010 –  /2) cos 2  ] 2 /2r B  = B 010  [ (B 010 –  /2) cos 2  ] 2 /2r a : Fixed to the values derived from the rotational analysis of the origin bands.

A 2  + (000) X 2  (010)  2 2  2 2 2r2r Energy difference between  2  and  2  Energy difference : 2r Energy difference : 2r 2r = [ A eff 2 + (2  2 ) 2 ] 1/2 =  -  2 79 r = (24) cm r = (30) cm -1   2r > |A eff | (= cm -1 ) Small influence of the Renner-Teller effect on the X 2  state of BrCN +

Renner parameter  p = 4B 010  2 /2r p = 4B 010  2 /2r state constant 79 BrCN + 81 BrCN +  2  p  (27)  (32)  2  p  (46)  (52) B (23) (25) 2r (24) (30)  (20) a 79  =  (27) 81  =  (32)  : Renner parameter p :  –  type doubling constant p :  –  type doubling constant BO 2 (X 2  )  =  0.19 CO 2 + (X 2  u )  =  a : Low resolution emission spectroscopy (Fulara et al.)

Wave functions for  2  and  2  Wave functions for  2  and  2  sin 2  =  2 /2 cos 2  = A eff /2 sin 2  : cos 2  = : Large spin-orbit interaction ! Influence of the Renner-Teller effect on the X 2  state of BrCN + is small !

Summary A 2  + - X 2  transition 1. Near-infrared emission spectrum of the A 2  + - X 2  transition of the BrCN + ionFT spectroscopy. BrCN + ion was observed by FT spectroscopy. Rotational analysis 2. Rotational analysis of the four bands, A 2  + (000) - X 2   (000) (  =3/2 and 1/2 ) A 2  + (000) -  2  and A 2  + (000) -  2 , A 2  + (000) -  2  and A 2  + (000) -  2 , was performed to determine the molecular constants. geometrical difference 3. The r 0 -structures of BrCN + were obtained and geometrical difference between BrCN and BrCN + was small. between BrCN and BrCN + was small. Renner parameter  =  Renner parameter was determined to be  =  0.185, and the influence of the Renner-Teller effect on X 2  was turned out large spin-orbit interaction to be small due to the large spin-orbit interaction.

Observed spectrum Nine vibronic bands of the A 2  + - X 2   transition Four vibronic bands of the A 2  + - X 2   transition A 2  + X 2  (000) (100) (010) (001) (100) (010) (001) 22 22 2   2   0 1,000 2,000 3,000 13,697 cm -1

BrCN + ion Renner-Teller effect Splitting of the vibronic state by the excitation of the bending vibration X 2  Electronic ground state : X 2  spin-orbit interaction Introduction Vibronic interaction

V + = a ( 1 +  ) (  r) 2 + … V - = a ( 1 –  ) (  r) 2 + … |  |<1|  |>1 NCO, N 2 O + ( X 2  ) NH 2 ( X 2 B 1, A 2  )  : Renner parameter Bending potential function

Molecular constants (unit : cm -1 ) state constant FT + D.L. D.L. LIF A 2  + 3/ (13) B (51) 10 7 D 0.346(16)  (37) X 2   B 3/ (47) (41) (47) 10 7 D 0.307(15) 0.158(23) 0.86(28) state constant FT + D.L. D.L. LIF A 2  + 3/ (13) B (50) 10 7 D 0.299(16)  (37) X 2   B 3/ (47) (11) (86) 10 7 D 0.262(14) 0.147(60) 1.5(56) 79 BrCN + 81 BrCN + eff A 2  + (000) – X 2  3/2 (000) transition

Molecular constants (unit : cm -1 ) state constant 79 BrCN + 81 BrCN + A 2  + 1/ (46) (59) B a a 10 7 D a a  a  a X 2   B 1/ (62) (67) 10 7 D 0.347(11) 0.214(16) p/2 + q (11) (15) eff 79 B 000 = (32) cm B 000 = (41) cm -1 Rotational constant B 000 B 3/2 = B 000 ( 1 + B 000 /A ) B 1/2 = B 000 ( 1  B 000 /A ) eff A 2  + (000) – X 2  1/2 (000) transition

Molecular constants (unit : cm -1 ) state constant 79 BrCN + 81 BrCN + A 2  +  (12) (17) B a a 10 7 D a a  a  a  2  B  (19) (26) 10 7 D (60) (79) p  (27)  (32) A 2  + -  2  state constant 79 BrCN + 81 BrCN + A 2  +  (21) (25) B a a 10 7 D a a  a  a  2  B  (25) (28) 10 7 D (58) (66) p  (46)  (52) A 2  + -  2 

Spin-orbit interaction constant A = 1/2 – 3/2 79 A =  (48) cm A =  (60) cm -1 X 2  (000) A 2  + (000) X 2   X 2   3/2 1/2 A low resolution emission spectroscopy A =  1477 cm -1

A 2  + (000) - X 2  1/2 (000) transition P 2 + Q 12 R 12 + Q 2 P 12 R2R2

A 2  + -  2  transition P1P1 R1R1 P 21 R 21

Renner parameter species A eff  2  79 BrCN +   (70)  (27) BO 2   86.4  0.19 CNC CO 2 +   96.8  NCO   76  0.14 N 2 O +   79.7 