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					Atomic and molecular spectroscopy with UV and Visible
                 superbright LEDs

     Ticijana Ban, Hrvoje Skenderović and Goran Pichler
Institute of Physics, Bijenička cesta 46, P. O. Box 304, HR-10001 Zagreb, Croatia


        Our most recent absorption and emission experiments
with heavy alkali vapor using superbright light emitting diodes
from NICHIA, LUMILED and OSRAM will be presented. UV
LEDs together with LEDs in the visible spectral region
present invaluable narrow band continuum light source for
very precise absorption measurements. We used all-
sapphire cells in a usual absorption arrangement high
resolution scanning monochromators. Beside self-broadened
alkali resonance lines we investigated molecular bands and
diffuse bands of alkali dimers similar to experiment in ref. (1).
A number of applications, especially in dentistry will be also
presented.
                              1 --- I=30 mA                      2
                        1.5   2 --- I=100 mA

                                                             1                               2



                                               2
Intensity / arb.units




                        1.0

                              380 nm
                                               1
                                                                                         1


                        0.5




                        0.0

                                  400          450   500             550     600   650           700
                                                           Wavelength / nm
                         7                                                                                           0,7

                                   wp=50 ns                              sg =5 kHz
                                                                                                                                                          Pulse width=10 s
                         6                                                                                           0,6
                                                                         Ip=91 mA                                                                         Ip=90 mA
                                      wp=30 ns
                         5                                                                                           0,5
                                                                                                                                 sg=20 kHz
intensity / arb. units




                                                                                            Intensity / arb. units
                         4                                                                                           0,4

                                                                                                                                 sg=10 kHz
                         3                                                                                           0,3

                                          wp=10 ns
                         2                                                                                           0,2         sg=5 kHz


                         1                                                                                           0,1



                         0                                                                                           0,0
                             400                  450              500                550                                  400                450              500            550
                                                 Wavelength / nm                                                                              doc -open %B%A




                             Spectral change of blue LED with UV component at different repetition rate
                               and different pulse width, at constant pulsed electric current of 90 mA.
                         0,05

                                                         violet LED

                         0,04
intensity / arb. units




                         0,03     NICHIA NSHU590E
                                  ILED=20 mA


                         0,02



                         0,01



                         0,00


                            360     370   380    390     400     410    420   430   440
                                                         / nm

                                      UV and violet light emitting diodes
Absorption experiment in rubidium vapor with NICHIA UV-LED
      as a background source with a possibility to measure
    fluorescence induced by NICHIA violet laser at 420 nm.
                                                                               Cs 8p-6s


                                                                      0,05                                Transmission spectrum of
                                                                                                          UV/blue LED through Cs vapor
  Transmission spectra at four




                                    Transmitted intensity / arb. u.
                                                                      0,04
      different temperatures                                                               291 C
                                                                                                 o

                                                                                                                                        o
      in the all-sapphire cell                                                                                                   535 C
                                                                                                                                        o
                                                                      0,03                                                       476 C
  filled with cesium saturated
                                                                                                                                        o
        vapor (T=291 oC),                                                                                                        424 C
                                                                      0,02
      and superheated vapor                                                                                                                       Cs 7p-6s

     (T= 424, 476, 535 oC).
                                                                      0,01                           K 5p-4s
                                                                                                                                 Cs 6d-6s

                                                                                                               Rb 6p-5s


                                                                      0,00
                                                                             380     390   400          410    420        430    440        450       460    470   480
                                                                                                                       / nm




                                                                       0.4

 Absorption coefficient in the
                                                                                           Cs2 UV/blue LED absorption
   380-480 nm spectral range
                                                                       0.3
 at four different temperatures
  in the all-sapphire cell filled
                                    -1
                                     k / cm




                                                                                                                                   o
                                                                                                                                424 C
 with cesium saturated vapor                                           0.2                                                          o
(T=291 oC), and superheated                                                                                                     476 C
                                                                                                                                    o
vapor (T= 424, 476, 535 oC).                                                                                                    535 C

                                                                       0.1




                                                                       0.0
                                                                             380     390   400          410    420        430    440        450       460    470   480

                                                                                                                      / nm
                                                                    Li2 A-X band absorption
                                                                    with red LED
                                                                                                              10


                    1,5
                                      o
                                T=710 C                             Io
                                wp=10 s                                                                           8

                                sg=10 kHz




                                                                                     -1
                                                                                      Absorption coefficient / m
                                Ip=105 mA
Intensity / arb. units




                                                                    I
                    1,0                                                                                            6




                                                                                                                   4


                    0,5

                                                                                                                   2
                                               atomic
                                               absorption

                    0,0                                                                                            0
                          620   630   640    650   660      670   680    690   700                                  620   630   640   650   660   670   680   690   700

                                             Wavelength / nm                                                                          Wavelength / nm
                                                                         Li2 B-X band absorption
                                                                         with green LED
                         2,0                                                                               10


                                                              Io

                                     o                        I                                                     8
                               T=710 C
                         1,5   wp=10 s




                                                                                      -1
                               sg=10 kHz




                                                                                       Absorption coefficient / m
                               Ip=105 mA
intensity / arb. units




                                                                                                                    6



                         1,0
                                                                                                                    4




                         0,5                                                                                        2




                                                                                                                    0

                         0,0
                               460       480     500    520        540    560   580                                     470   480   490   500   510    520   530   540
                                               Wavelength / nm                                                                       Wavelength / nm
                                                   Li2 POTENTIAL CURVES

                   20
                   18
                                                                                   2       2
                   16                                                          Li(2 S)+Li(2 P)
                   14
                                                     1
                   12                              B u
                   10
-1




                    8
 Energy / *10 cm
3




                    6
                                                     1 +
                    4                              A        u
                                       GREEN LED


                    2
                             RED LED




                                                                                   2       2
                                                                               Li(2 S)+Li(2 S)
                    0
                    -2
                    -4
                    -6
                                                    1 +
                    -8                             X    g
                   -10
                         2             3                 4        5    6   7           8         9
                                                                 R/A
                                                                                                                             13.03.02.
                                                                                                                        w=80 m, HV=610 V
                      0,05
                                                                                                 1,0

                                                                                                                                                              K, 5p1/2 - 4s1/2
                                                 405,2152                                                                                  K, 5p3/2 - 4s1/2
                                                                                                 0,8




                                                               Transmitted intensity / arb. u.
                      0,04                                                                                    T = 612 C
                                                                                                                        o
intensity / arb. u.




                                                                                                 0,6
                                                                                                             Johnson (PhD, 1985)


                                                                                                 0,4                                 402.5 nm
                                                                                                                                   K2 long-range
                      0,03                                                                                                         satellite band

                                                                                                 0,2




                                                                                                 0,0
                      0,02                                                                             396        398       400      402             404             406         408

                                                                                                                                        / nm




                      0,01



                      0,00
                         375 380 385 390 395 400 405 410 415 420 425 430 435 440
                                                       / nm

                       Violet LED continuum is ideal for absorption of a second potassium doublet
                                    300   350    400     450       500    550
                                    8                                       8




                                            CQ(absorption)
                                    6                                       6



           Intensity (rel. units)


                                    4                                       4




                                    2                                       2




                                                        NSPB500, 30 mA,
                                    0                                       0
                                    300   350    400     450       500    550

                                                  wavelength (nm)


Almost perfect match between blue LED and Camphorquinone absorption used
         for photoplymerization of composite materials in dentistry.

				
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posted:9/22/2011
language:Croatian
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