Laser Induced Fluorescence Spectroscopy of the JetCooled Transient

Laser Induced Fluorescence Spectroscopy of the Jet-Cooled Transient Species As. D 2 and As. HD Bob Grimminger and Dennis Clouthier Department of Chemistry, University of Kentucky, Lexington, KY

Motivation As. H 3 is used in many semiconductor processes but species involved are not well understood Dixon et al. (Proc. Roy. Soc. A. 305, 271 (1968)) only partially studied As. D 2 at low resolution Continuation of As. H 2 study by Clouthier group Measurement of new vibrational frequencies of interest 2

Production of jet-cooled radicals Precursor gas mix: 3% As. D 3 in Ar 3

Preliminary information � Ground state constants known from microwave study (H. Fujiwara and S. Saito, J. Mol. Spec. 192, 399 (1998). ) � Excited state constants for As. H 2 isotopologue known from previous work in Clouthier lab (S. -G. He and D. J. Clouthier, J. Chem. Phys. 126, 154312, (2007). ) � Estimate of origin from previous As. D 2 study � Arsenic has a nuclear spin of 3/2 � Near oblate in ground state; near prolate in excited state 4

Vibronic analysis of As. D 2 LIF spectrum Parameter Observed ω1 (cm-1) ω2 (cm-1) ω3 (cm-1) 5 Calculated 1679. 8 612 (2) 613. 7 1600. 1 B 3 LYP/Aug-cc-p. VTZ

High resolution spectrum of the 0 -0 band Experimental Simulation from fit 6

Comparison of excited state rotational constants 7 Excited state parameter As. D 2 As. H 2 A (cm-1) 8. 730 9 (5) 17. 2065 (13) B (cm-1) 2. 468 7 (2) 4. 9196 (6) C (cm-1) 1. 895 4 (3) 3. 7404 (6) εaa (cm-1) 2. 329 (3) 4. 718 (4) εbb (cm-1) 0. 044 3 (15) 0. 082 (3) εcc (cm-1) -0. 109 2 (19) -0. 202 (3) εaa/A 0. 2668 (3) 0. 2741 (4) εbb/B 0. 0179 (2) 0. 016 8 (3) εcc/C -0. 058 (1) -0. 0542 (8)

Ground and excited state geometries Ground state geometry determined by microwave study Excited state geometry refined from observed rotational constants from both isotopologues Ground statea Excited stateb As-H (Å) 1. 5158 (6) 1. 483 (5) H-As-H (degrees) 90. 79 (8) 122. 9 (2) H. Fujiwara and S. Saito, J. Mol. Spec. 192, 399 (1998). b This work. a 8 Coordinate

Resolved resolved hyperfine splittings 9

Hyperfine constants in the excited state 10 Parameter As. D 2 As. H 2 a. F (As) (cm-1) . 0567 (11) . 0511 (14) aa 1 (As) (cm-1) -0. 0087 (28) bb 1 (As) (cm-1) 0. 0168 (36)

Single level emission from As. D 2 Ka´ = 1 Ka´´ = 2 Ka´´ = 0 ω2 = 707 (1) cm-1 x 22 = -2. 0 (2) cm-1 11

Single level emission from As. HD ω2 = 862. 4 (8) cm-1 x 22 = -4. 0 (2) cm-1 12

Ground state vibrational frequencies for various isotopologues Parameter As. H 2 a As. D 2 b As. HDb ω1 (cm-1) (observed) 2096. 5 (9) -- -- 2172. 6 1546. 3 2178. 3 984. 4 (6) 707 (1) 862. 4 (8) 1003. 5 714. 7 871. 1 -- -- -- 2184. 1 1555. 3 1550. 9 (calcul ated) ω2 (cm-1) (obs. ) (calc. ) ω3 (cm-1) (obs. ) (calc. ) 13 a Previous Clouthier study b This work

Geometry comparison of isovalent species Ground state Excited state NH 2 a PH 2 a As. H 2 b Angle (deg. ) 103. 4 91. 7 90. 79 (8) Bond length (Å) 1. 024 1. 418 1. 5158 (6) Angle (deg. ) 144 123. 2 122. 9 (2) Bond length (Å) 1. 004 1. 389 1. 483 (5) D. A. Ramsay in Spectroscopy of the Excited State, edited by B. Di Bartolo (Plenum Publishing Corp. , New York, 1976) p. 66. b Fujiwara (1998) and this work. a 14 Parameter

Conclusions Accurate determination of the excited state constants of As. D 2, allowing for the refinement of the excited state geometry Determination of bending vibrational frequencies of As. D 2 in ground and excited states First reported spectra of As. HD 15