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Polarization enhanced NQR detection at low frequencies

Polarization enhanced NQR detection at low frequencies. Janko Luznik. Institute of Mathematics, Physics and Mechanics, Ljubljana. EUROMAR 2008, Saint Petersburg, Russia, 6-11 July 2008. TNT,  Q  850 kHz, low signal/noise , RF sensitivity  

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Polarization enhanced NQR detection at low frequencies

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  1. Polarization enhanced NQR detection at low frequencies Janko Luznik Institute of Mathematics, Physics and Mechanics, Ljubljana EUROMAR 2008, Saint Petersburg, Russia, 6-11 July 2008

  2. TNT, Q  850 kHz, low signal/noise, RF sensitivity   Signal intensity  N Boltzmann distribution N  exp(-E/kT) ; N E/kT; E = h ; N  Proton polarization H Q NH NQ EUROMAR 2008, Saint Petersburg, Russia, 6-11 July 2008

  3.  = NN/(NH+NN) EUROMAR 2008, Saint Petersburg, Russia, 6-11 July 2008

  4. For the spin 1 14N nuclei energy levels and allowed transitions are: Q is the nuclear electric quadrupole moment,q the maximal component of EFG tensor is the asymmetry parameter. EUROMAR 2008, Saint Petersburg, Russia, 6-11 July 2008

  5. EUROMAR 2008, Saint Petersburg, Russia, 6-11 July 2008

  6. EF+= DN3+/DN0+=(++a+b/2+g/2)/ + EF-= DN3-/DN0-=(-+a/2+b-g/2)/ - EF0= DN30/DN00=(0+a/2-b/2+g)/ 0 EUROMAR 2008, Saint Petersburg, Russia, 6-11 July 2008

  7. TNT Two molecules per unit cell – 6 +, 6- and 60 frequencies two modifications: monoclinic and orthorhombic

  8. Zeeman broadening of the + lines for B  20 mT (nH  850 kHz) and - lines for B  17.5 mT (nH  750 kHz) in TNT EUROMAR 2008, Saint Petersburg, Russia, 6-11 July 2008

  9. For TNT  = 2/7 EF0 EF+  50/T EF- EUROMAR 2008, Saint Petersburg, Russia, 6-11 July 2008

  10. proton-nitrogen spin coupling in TNTNH 500 Hz Tcp>> 1/ NH= 2 ms proton NMR linewidth His around 20 kHz (0.5 mT) dB/dt  0,5 mT/2 ms = 250 mT/s The signal intensity enhancement factor for the + (870 kHz) line in TNT at room temperature. EUROMAR 2008, Saint Petersburg, Russia, 6-11 July 2008

  11. multi-pulse pulse spin-locking sequence a0 - ( t - a90- t - )n EUROMAR 2008, Saint Petersburg, Russia, 6-11 July 2008

  12. + part of 14N NQR spectrum in an old sample of TNT where the mixture of two phases monoclinic/orthorhombic (approx. 50%/50%) can clearly be resolved. EUROMAR 2008, Saint Petersburg, Russia, 6-11 July 2008

  13. EUROMAR 2008, Saint Petersburg, Russia, 6-11 July 2008

  14. EUROMAR 2008, Saint Petersburg, Russia, 6-11 July 2008

  15.  = 1000s, 50x  = 200s, 300x EUROMAR 2008, Saint Petersburg, Russia, 6-11 July 2008

  16. Conclusions • Polarization enhancement can be very effective • reduction of detection time • strong polarizing magnetic field is needed • nonhomogenous field (average field) • ratio of protons to nitrogens • proton relaxation time • nitrogen relaxation time EUROMAR 2008, Saint Petersburg, Russia, 6-11 July 2008

  17. Faculty of mathematics and physics Institute of Mathematics, Physics and Mechanics, Ljubljana Janez Pirnat Vojko Jazbinsek Janko Luznik Zvonko Trontelj Janez Seliger Tomaz Apih Robert Blinc Alan Gregorovic EUROMAR 2008, Saint Petersburg, Russia, 6-11 July 2008

  18. EUROMAR 2008, Saint Petersburg, Russia, 6-11 July 2008

  19. EUROMAR 2008, Saint Petersburg, Russia, 6-11 July 2008

  20. EUROMAR 2008, Saint Petersburg, Russia, 6-11 July 2008

  21. The multi-pulse pulse spin-locking (PSL) a0 - ( t - a90 - t - )n EUROMAR 2008, Saint Petersburg, Russia, 6-11 July 2008

  22. S(n) = a O(n) + b M(n) EUROMAR 2008, Saint Petersburg, Russia, 6-11 July 2008

  23. 50:50 1937 1955 EUROMAR 2008, Saint Petersburg, Russia, 6-11 July 2008

  24. TNT six +lines average 10000 X  few 10 hrs RDX + line at 5256 kHz single shot  10 msec

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