1. The Rotational Spectrum and Hyperfine Constants of Arsenic Monophosphide, AsP Flora Leung, Stephen A. Cooke and Michael C. L. Gerry Department of Chemistry, The University of British Columbia, 2036 Main Mall, Vancouver, B. C. Canada, V6T 1Z1

2. Introduction All intergroup 15 diatomics have been spectroscopically studied. Hyperfine structure for PN (a), SbN, SbP (b), BiN, BiP (c) has been observed. AsP 1969: 12 red-degraded bands were observed. Suggested to be the 1  - X 1  system. (d) 1970: Rotational analysis of the observed bands. (e) a Raymonda & Klemperer, J. Chem. Phys. 1971, 55, 232 b Cooke & Gerry, PCCP, 2004, 6, 4579 c Cooke, Michaud & Gerry, J. Mol. Struct. 2004, 695, 13 d Yee & Jones, Chem. Comm. 1969, 586 e Harding, Jones & Yee, Can. J. Phys. 1970, 48, 2842

5. Prediction of AsP Transition Frequencies. Based on rotational constant of Harding, Yee and Jones, B e = 5771 MHz. DFT QZ4P/SAOP calculations provided an estimate for eQq( 75 As) = -247.7 MHz

6. AsP Portion of spectra shown required 1000 avg. cycles and is displayed as a 4k transformation. Transitions shown are from J = 1 - 0 rotational transition. The group on the left is from within the v = 0 state, that on the right from within the v = 1 state.

7. Data Set AsP has only one isotopomer. Hyperfine structure from As (nuclear spin, I = 3/2). Magnetic hyperfine structure from P (nuclear spin, I = 1/2). J = 1 - 0 and 2 - 1 transitions were observed in the vibrational ground state and first excited vibrational state.

8. Equilibrium Spectroscopic Parameters for AsP

9. Equilibrium Bond Lengths of Group V Phosphides AsP equilibrium bond length : r e (AsP) = 1.99954398(16) Å a Ahmed & Hamilton, JMS, 1995, 169, p.286 b Rao & Laksham, IJPAP, 1970, 8, p.617 C Cooke & Gerry, PCCP, 2004, 6, p.4579 d Cooke, Michaud & Gerry, J. Mol. Struct, 2004, 695-696, p.13 r(P-H) in PH3 = 1.42Å

10. “Triple-bond covalent radii” 0.54 Å 0.94 Å 1.06 Å 1.27 Å 1.35 Å Pekka Pyykkö, Sebastian Riedel and Michael Patzschke Chemistry: A European Journal, 2005, 11, p.3511 “A coherent bond length amplified by some  2  4 character in the wave function will form an entrance ticket to the data set”

11. Empirical Relationships for AsP: a Harding, Jones & Yee, Can. J. Phys. 1970, 48, 2842

12. Force Constants and Dissociation Energies for the Group 15 Phosphides For AsP: k = 507 Nm -1 and E diss. = 576(40) kJ mol -1 lit. val. D 0 0 = 430 kJ mol -1 (a) a Gingerich, Cocke & Kordis, J. Phys. Chem. 1974, 78, 603

13. Force Constants and Dissociation Energies for the Group 15 Phosphides BiP SbP AsP P2P2 PN P2P2 AsP SbP BiP For the Morse potential k = 2  2 E diss. a Gingerich, Cocke & Kordis, J. Phys. Chem. 1974, 78, 603

14. Hyperfine Constants

15. eQq e ( 75 As) value in AsP = -249.0963(75) MHz (DFT value = -247.7 MHz) a Using most recent literature value for Q, (= -66.9(15) fm 2 ): Svane, Phys. Rev. B, 2003, 68, 64422. b Using Q (= -36(4) fm 2 ) value tabulated by Pyykko, Mol. Phys. 2001, 99, 1617.

16. PNAsPSbPBiP Field Gradients at the non-phosphorus nucleus in the group V phosphides. (PP) Using DFT we calculated q at Sb in SbP to be - 4.7  10 22 V m -1. Our results suggests a better value for Q( 121 Sb) of ~ 50 fm 2. Using Q( 121 Sb) = -66 fm 2 Using Q( 121 Sb) = -36 fm 2

17. Vibrational Dependence of eQq For all of the group V phosphides for which appropriate data is available: Electronic ground states have asymptotes corresponding to atomic ground states of 4 S 3/2 for both atoms (i.e. an s 2 p 3 configuration) a. Increase in v → step toward this asymptote, at which point q at each atom is zero. |eQq| ↓ as v ↑ a Alekseyev, Liebermann, Hirsch & Buenker, Chem. Phys. 1997, 225, p247 eQq v=0 ( 75 As) = -247.9495(46) eQq v=1 ( 75 As) = -245.6560(61)

18. 31 P Nuclear Spin-Rotation Constants a Ahmed & Hamilton, JMS, 1995, 169, p.286 b Raymonda & Klemperer, JCP, 1971,55, p.232 C Cooke & Gerry, PCCP, 2004, 6, p.4579 d Cooke, Michaud & Gerry, J. Mol. Struct, 2004, 695-696, p.13

19. Ab initio Value Toscano et al. ZPD, 1992, 22, p683 31 P Nuclear Spin-Rotation Constants 10 6 C I (P) / B e 3  + - 1  + Energy Separation / cm -1 PN AsP SbP BiP Where W 1 - W 0 is the energy gap between the ground and first excited electronic states, a 3  + - X 1  +. Expt’l values: Rasanen et al. JCP, 1986, 85, p86 Briedohr et al. JMS, 1995, 172, p369

20. C I nuc depends only on the nuclear positions. C I elec depends on the ground and excited state wave functions. Similarly:  av =  p +  d  d depends on the ground state wave function.  p is directly proportional to C I el. The relationship between C I and shielding constants Flygare & Goodison:

21. As and P Nuclear Spin-Rotation Coupling Constants More directly C I may be related to the span of the shielding tensor: 75 As 31 P C I / kHz 25.6(7) 23.6(2)  p / ppm -2895(74) -1262(8)  d / ppm 2920 1112  av / ppm 25 -150  / ppm 4070(110) 3756(29)  calc. / ppm 5061 2391 C I calc. / kHz 30.4 33.9 DFT calc.

22. Conclusions The pure rotational spectrum of AsP has been recorded for the first time. eQq( 75 As) has been determined in AsP and compared with other known eQq values in related molecules. The comparison suggests an anomaly in Q(Sb). Nuclear spin-rotation coupling constants have provided useful electronic structure information for the series of Group 15 phosphides.

23. Acknowledgements UBC Mech. And Elec. Workshops The Natural Sciences and Engineering Research Council of Canada (NSERC)