Lyuminisensiya PhD. Kenjayev D. R

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Molecular Luminescence Spectroscopy

Lyuminisensiya

Moddalar, atomlar, molekulalar yoki ionlarning turli xil qo’zg’atuvchi omillar ta’sirida shu’lalanishi lyuminisensiya deyiladi.

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Agar nurlanish ultrabinafsha va ko’rinadigan nurlar sohasiga to’g’ri keladigan nurlanish ta’sirida yuzaga kelsa, bunday lyuminisensiya ftolyuminisensiya deyiladi.

Chiqadigan nurlanish to’lqin uzunligi yutilganidan kattaroq bo’ladi. Chunki uning bir qismi issiqlik sifatida tarqatiladi.

Tarmoqli bo'shliqni aniqlash. Yarimo'tkazgichlarda eng keng tarqalgan radiatsion o'tish o'tkazuvchanlik va valentlik diapazonidagi holatlar o'rtasida bo'lib, energiya farqi tarmoqli oralig'i deb nomlanadi.

Nopoklik darajasi va nuqsonlarni aniqlash. Yarimo'tkazgichlarda radiatsion o'tishlar lokalizatsiya qilingan nuqson darajasini ham o'z ichiga oladi. Ushbu darajalar bilan bog'liq bo'lgan fotoluminesans energiyasidan ma'lum nuqsonlarni aniqlash uchun foydalanish mumkin.

Lyuminisensiya spektri doimo yutilish spekrtidan o’ngroqqa siljigan bo’lib, ko;pchilik moddalar uchun bu ko’zgu simmetriyasi shaklida bo’ladi. Bu maksimumlar orasidagi farq stoks siljishi deb ataladi.

Paulini chiqarib tashlash printsipi atomdagi hech qanday ikkita elektron to'rtta kvant sonining bir xil to'plamiga ega bo'lolmasligini aytadi. Ushbu cheklov spin holatiga ikkitadan ko'p bo'lmagan bo'lishi kerakligini talab qiladi. Spin juftligi tufayli ko'pgina molekulalar aniq magnit maydonni namoyish etmaydi va shuning uchun diamagnetik deyiladi. Aksincha, tarkibida juft bo'lmagan elektronlarni o'z ichiga olgan erkin radikalning magnit momenti paramagnitik deyiladi.

Barcha elektron spinlari juftlashgan molekulyar elektronlar holatiga singlet holat deyiladi va molekula magnit maydon ta'sirida elektron energiya darajalarining bo'linishi bo'lmaydi.

Erkin radikalning asosiy holati esa dublet holatidir, chunki toq elektron magnit maydonida ikkita yo'nalishni qabul qilishi mumkin, bu tizimga bir oz boshqacha energiya beradi

Foton nurlanishining yutilish tezligi juda katta, bu jarayon 10-14 dan 10-15 sek oralig’ida. Boshqa tomondan, lyuminestsentsiya emissiyasi sezilarli darajada past darajada sodir bo'ladi. Bu erda qo'zg'aladigan holatning davom etish jarayoni qo'zg'alish jarayoniga mos keladigan yutilish cho'qqisining molyar yutish qobiliyatiga teskari bog'liqdir..

Muayyan ta’sirlar ostida lyuminisensiya jarayoni kamayadi. Bu hodisa so’nish deb ataladi.

Molekulyar tuzilish ham, kimyoviy muhit ham moddaning porlashi yoki yo'q bo'lishiga ta'sir qiladi; lyuminesans paydo bo'lganda bu omillar ham emissiya intensivligini aniqlaydi.

Sources: A more intense source in needed than the tungsten of hydrogen lamp.
Lamps: The most common source for filter fluorometer is a low-pressure mercury vapor lamp equipped with a fused silica window. For spectrofluorometers, a 75 to 450-W high-pressure xenon arc lamp in commonly employed.
Lasers: Most commercial spectrofluorometers utilize lamp sources because they are less expensive and less troublesome to use.

Filters and Monochromators: Both interface and absorption filters have been used in fluorometers for wavelength selection of both the excitation beam and the resulting fluorescence radiation. Most spectrofluorometers are equipped with at least one and sometimes two grating monochromators.
Transducers: Photomultiplier tubes are the most common transducers in sensitive fluorescence instruments.
Cell and Cell Compartments: Both cylindrical and rectangular cell fabricated of glass or silica are employed for fluorescence measurements.

http://www.acs.org
http://www.cas.org
http://www.chemcenter/org
http://www.sciencemag.org
http://www.kerouac.pharm.uky.edu/asrg/wave/wavehp.html
http://www.chemistry.msu.edu/courses/cem333/Chapter%2015%20-%20Molecular%20Luminescence%20Spectrometry.pdf
http://elchem.kaist.ac.kr/vt/chem-ed/spec/molec/mol-fluo.htm
http://www.shsu.edu/~chm_tgc/chemilumdir/chemiluminescence2.html

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