ACS, April 2008 p. 1/26 Cold molecule studies of OH, NH, and metastable CO Gerrit C. Groenenboom Theoretical Chemistry Institute for Molecules and Materials Radboud University Nijmegen The Netherlands
ACS, April 2008 p. 2/26 Collaborators OH, CO: FHI Berlin Joop Gilijamse Steven Hoekstra Samuel Meek Markus Metsälä Bas van de Meerakker Gerard Meijer NH: Harvard Wes Campbell Hsin-I Lu Edem Tsikata John Doyle
ACS, April 2008 p. 3/26 Cold molecule techniques 1998 buffergas cooling John Doyle, CaH 1999 Stark deceleration Gerard Meijer, CO 2001 rotating nozzle Dudley Herschbach, O 2 2001 storage ring Gerard Meijer, ND 3 2002 photoassociation Pierre Pillet, Cs 2 (trapped) 2003 filtering Gerard Rempe, NH 3 2003 Feshbach resonances Rudy Grimm, Li 2 (BEC) 2003 billiard ball collisions Dave Chandler, Ar+NO 2004 optical Stark deceleration Peter Barker, C 6 H 6 2007 reactive collision slowing Hans-Joachim Loesch, K+HBr 2007 Zeeman deceleration Nicolas Vanhaeke, H 2007 molecular synchrotron Gerard Meijer, NH 3... cavity laser cooling Yun Ye, OH (theory)... sympathetic cooling Peter Barker
ACS, April 2008 p. 4/26 Xe+OH( 2 Π 3/2f ) collision experiment cooled -70 o C LIF zone PMT Xe Stark decelerator skimmer hexapole detection laser (282 nm) pulsed valve photodissociation laser (193 nm) Bas van de Meerakker, Steven Hoekstra, Joop Gilijamse, Gerard Meijer (Berlin, 2006)
ACS, April 2008 p. 5/26 OH X( 2 Π) energy levels cm -1 250 200 3 7/2 f e + - 2 3/2 f + e - 150 100 50 2 5/2 f e - + 1 1/2 N J F 2, X 2 Π 1/2 f - e + ε p 0 1 3/2 N J f + e - ε p F 1, X 2 Π 3/2
Xe OH( 2 Π) potentials (cm 1 ) Xe OH (A ) Xe OH (A ) 180 180 50 100 100 1450 1450 150 120 90 60 30 75 125 650 75 75 450 50 50 50 θ (degrees) 150 200 175 150 120 90 60 30 θ (degrees) 100 25 850 25 125 850 150 450 200 5 6 7 8 9 10 11 12 R (a 0 ) 175 0 4 6 8 10 12 0 R (a 0 ) Molpro: RCCSD(T), aug-cc-pvqz+bond orbitals, ECP28MDF ACS, April 2008 p. 6/26
ACS, April 2008 p. 7/26 Xe+OH energy dependent cross sections 10 3 F 1 (3/2f) 10 2 F 1 (3/2e) σ (Å 2 ) 10 1 10 0 F (5/2e) 1 F (1/2) 2 F (7/2) 1 F (5/2f) 1 F (3/2) 2 0 100 200 300 400 E coll (cm 1 )
Xe+OH experimental results ACS, April 2008 p. 8/26
ACS, April 2008 p. 9/26 Xe+OH, comparison with experiment 100 σ (%) 80 60 40 20 F 1 (3/2e) F 1 (5/2e) F 1 (5/2f) 0 F 2 (1/2e) 50 100 150 200 250 300 350 400 E coll (cm 1 ) Gilijamse, Hoekstra, van de Meerakker, Groenenboom, Meijer, Science 313, 1617 (2006)
ACS, April 2008 p. 10/26 Xe+OH, convolution and Xe beam σ(e coll ) voh 2 Signal n OH n + v2 Xe Xe v OH 350 340 4 3.5 4.5 4 5 4.5 5.5 5 v Xe (m/s) 330 320 310 300 3 3 3.5 44 3.5 3.5 3.5 4 290 4.5 4 280 270 5 5.5 4.5 4.5 5 5 10 15 20 25 30 35 FWHM (%) 5
ACS, April 2008 p. 11/26 Convergence check Xe+OH: F max 10 0 10 2 10 4 10 6 3/2e 3/2f 5/2e 5/2f 1/2e 1/2f 10 8 0 20 40 60 80 100 120 F F l = 45 b = l 2µEcoll 8 bohr
ACS, April 2008 p. 12/26 Buffergas loading Buffer-gas Cooling and Loading Hot Molecules 1000 K Superconducting Magnet Coils Cold Walls < 1 K Helium Buffer Gas 10 15 cm -3 Cold Trapped Molecules John Doyle, Wes Campbell, et al., Harvard Accepts full Boltzmann distribution of source External motion, rotation thermalize quickly Vibration, spin thermalize slowly He provides dissipation in conservative trap potential
ACS, April 2008 p. 13/26 NH(v = 1) in trap vs time Number of Trapped NH(v"=1) [arb.] v=1 v"=1 A 3 Π 2 X 3 Σ - 50 100 150 200 250 300 Time [ms] W. C. Campbell, G. C. Groenenboom, H.-I Lu, E. Tsikata, and J. M. Doyle, Phys. Rev. Lett., 100, 083003 (2008)
ACS, April 2008 p. 14/26 Measured NH(v = 0, 1) trap lifetime Trapped Molecule Lifetime [ms] 350 300 250 200 150 100 50 v = 0 v = 1 0 0 2 4 6 8 10 12 14 16 18 Buffer-Gas Density [10 14 cm -3 ] W. C. Campbell, G. C. Groenenboom, H.-I Lu, E. Tsikata, and J. M. Doyle, Phys. Rev. Lett., 100, 083003 (2008)
ACS, April 2008 p. 15/26 NH X 3 Σ (v = 1) lifetime (ms) τ 1 = f 4αω 3 3c 2 v = 0,N = 1 µ(r) v = 1,N = 0 2 e2 Rosmus, Werner, 1980, PNO-CEPA 28.7 Dodd et al., 1991, MRCI/RKR 19.3 (23.9) CASSCF/MRCI aug-cc-pvtz 26.3 +rotation 29.1 +cc-pv6z 31.7 +active space (6σ, 3π) 35.1 +core-correlation 37.01 +aug-cc-pv6z 36.99 RHF+RCCSD(T) finite field 37.4 buffergas cooling experiment: 37.0 ± 0.5 ms
ACS, April 2008 p. 16/26 NH( 3 Σ ) permanent dipole moment (v = 0) Experiment, Scarl and Dalby (1974) 0.543± 0.028 ea 0 CASSCF+MRCI aug-cc-pv6z: 0.600 Paldus and Li (1996): 0.604 Conclusion: 30% more N on our sun
Radiative lifetime of OH X 2 Π 3/2 (v = 1) Van de Meerakker, Vanhaecke, van der Loo, Groenenboom, and Meijer, Phys. Rev. Lett., 95, 013003 (2005) ACS, April 2008 p. 17/26
ACS, April 2008 p. 18/26 Radiative lifetime of OH X 2 Π 3/2 (v = 1) Molpro: aug-cc-pv6z, 1σ 5σ, 1π 2π CASSCF/MRCI year τ (ms) Decay in trap 2006 59.0±2 Present calculation 2007 56.9 (57.2) HITRAN 2004 56.6 D. D. Nelson et al. 1990 55.7 S. R. Langhoff et al. 1989 57.8 S. R. Langhoff et al. 1986 81.3 H.-J. Werner et al. 1983 71.6 M. van der Loo and G. C. Groenenboom, J. Chem. Phys. 126, 114314 (2007)+erratum Application to OH Meinel system: Decrease in atomic hydrogen over the summer pole, D. E. Siskind et al., Geophys. Res. Lett. (2008), submitted
ACS, April 2008 p. 19/26 CO(a 3 Π 1 ) lifetime model 50 40 h a (r) 1 cm 1 30 20 h A,a (r) µ X,A (r) 0.5 a.u. τ 1 = v X A vx,v a 10 0 0 1.5 2 2.5 3 ev 10 8 6 4 A( 1 Π) a( 3 Π) X( 1 Σ + ) A vx,v a = 4αω3 v a,v X 3c 2 e 2 c 2 Ω,1 v A v X µ X,A v A v A h A,a v a E va E va 2 0 1.5 2 2.5 3 r (a 0 ) Thomas James, JCP 1971
ACS, April 2008 p. 20/26 CO(a 3 Π 1 ) lifetime results (ms) Experiment: 2.63 ± 0.03 Thomas James (JCP 1971): 2.93 +11% Ab initio + RKR potentials: 3.16 +20% Sykora and Vidal (JCP 1999): 3.41 +30% Jongma, Berden, Meijer (JCP 1997): 3.67± 0.2 +40% 3.4± 0.5 +30% J. Gilijamse et al., J. Chem. Phys., 127, 221102 (2007)
ACS, April 2008 p. 21/26 CO(a 3 Π 1 ) lifetime extended model lower level calculation (MCSCF/aug-cc-pVTZ) extra 1 Π intermediate states result scaled to 3.16 ms for single intermediate state 1 3.16 ms 20.0% 2 3.34 ms 27.0% 3 2.69 ms 2.4% 4 2.90 ms 10.3% 5 2.72 ms 3.4% Experiment: 2.63 ms
ACS, April 2008 p. 22/26 Check of spin-orbit coupling CO (a 3 Π Ω ) v a Ab initio Experiment error (%) 0 40.801 41.429 1.51 1 40.668 41.266 1.45 2 40.489 41.082 1.45 3 40.302 40.887 1.45 4 40.107 40.704 1.49 5 39.902 40.502 1.51 6 39.687 40.245 1.42 7 39.462 40.019 1.43 8 39.228 39.781 1.43 9 38.985 39.329 0.92 R. W. Field et al., J. Mol. Spectrosc. (1972)
ACS, April 2008 p. 23/26 CO A 1 Π X 1 Σ + transition dipole moment µ X,A (ea 0 ) 1 0.75 0.5 present Spielfiedel (1999) Kirby (1989) EOM HF EOM MCSCF r = 2.0 a 0 r = 2.5 a 0 present (ea 0 ) 0.7835 0.4131 Spielfiedel [1] 91.6% 99.1% Kirby [2] 94.9% 99.6% 0.25 CCSD-EOM(HF) 93.4% 98.0% EOM(MCSCF) 93.6% 99.4% 0 1 2 3 4 r (a ) 0 [1] A. Spielfiedel et al., Astron. Astrophys. (1999) [2] K. Kirby and D. L. Cooper, J. Chem. Phys. (1989)
ACS, April 2008 p. 24/26 CO A 1 Π X 1 Σ + oscillator strength f osc = v A 2 3 (E v A E vx ) µ va,v X 2 Present 0.177 2.4% Experiment (1993) 0.181 Other experiments: 0.187 0.195 Spielfiedel (1999) 0.160 11.5% Kirby (1989) 0.167 7.5% W. F. Chan et al., Chem. Phys. (1993) Electron energy loss spectrosc. + TRK sum-rule (7-200 ev)
CO A 1 Π(v ) dependent lifetimes (ns) 10 9.5 Experiment Fit τ (ns) 9 8.5 Ab initio 8 0 1 2 3 4 5 6 7 v Experiment: R. W. Field et al., J. Chem. Phys. (1983) Using fitted dipole: τ(co a 3 Π 1 ) = 3.66 ms. ACS, April 2008 p. 25/26
ACS, April 2008 p. 26/26 Conclusions Xe+OH: towards crossed controlled beams NH(v = 1) lifetime: 30 % more N on our sun OH(v = 1) lifetime benchmark: Meinel system CO(a 3 Π 1 ) lifetime: nonorthogonality essential, measured A 1 Π(v ) lifetimes wrong