Fast photoprocesses in a symmetric indotricarbocyanine dye (hitc) in solutions

Spectral-kinetic and photochemical properties of HITC dye with iodide and perchlorate counterions have been studied in environments where the dye molecules exist in different ionic forms. In ethanol, the dye molecules exist as free ions; in dichlorobenzene, as contact ion pairs. Superfast transformation of non-stationary spectra in an HITC dye bleaching band is found. The observed effects are interpreted within the framework of concepts on "burning out" a notch in the contour of a non-uniformly widened vibronic band of S0 → S1-absorption. Qualitative differences in recorded absorption spectra from the dye excited electronic states for weakly and highly polar solvents are found. It is shown that the observed differences are caused by superfast charge transfer in the contact ion pairs that results in the formation of free radicals

Transient Absorption Phenomena in Synthetic HPHT and CVD Diamonds for a Fast Timing in Nuclear Instrumentation

In this study, we investigate  transient phenomena in synthetic diamonds  obtained by High Pressure High Temperature and Chemical Vapor Deposition methods. Study was aimed at searching for inorganic crystalline media combining ionizing radiation detecting properties and non-linear absorption of ultra-short laser pulses. The nonlinear pump-and-probe optical absorption technique with of 140 fs laser pulses was used to study the effects

Semiconductor A3B5 nanostructures for infrared femtosecond lasers

Two techniques were suggested and tested for the recovery time shortening of saturable absorbers on a base of A3B5 compounds including quantum wells. The first one, proposed by authors, is the sample post-growth treatment by UV laser radiation; it implied generation of point defects, which, in its turn, led to electron-hole recombination acceleration and to recovery time shortening by an order of magnitude and more. Another technique based on special design of barriers gave promising results for the fast saturable absorbers. Semiconductor mirrors designed for Yb3+:KY(WO4)2 infrared laser mode locking led to 115 fs stable modelocking regime with average power close to CW operation. Results on fast saturable absorbers for spectral region of 1500 nm are also presented

ИСПОЛЬЗОВАНИЕ ДВУХФОТОННОГО ПОГЛОЩЕНИЯ В НЕОРГАНИЧЕСКИХ СЦИНТИЛЛЯЦИОННЫХ МАТЕРИАЛАХ ДЛЯ ФОРМИРОВАНИЯ СУБПИКОСЕКУНДНЫХ ВРЕМЕННЫХ МЕТОК ВЗАИМОДЕЙСТВИЯ С ИОНИЗИРУЮЩИМ ИЗЛУЧЕНИЕМ

The features of the two-photon absorption signal in lead tungstate crystals (PbWO4) in the “pump – probe” experiment are considered. The differences in the spectral dependences of the recorded two-photon absorption effect in the presence of ionizing radiation of a crystal and without it are discovered. The method of utilizing the effect to generate a time stamp of interaction of ionizing radiation with a scintillator is proposed. Рассмотрены особенности сигнала двухфотонного поглощения в кристалле вольфрамата свинца (PbWO4) в эксперименте типа «накачка – зондирование». Обнаружены различия в спектральных зависимостях регистрируемого эффекта двухфотонного поглощения при наличии ионизирующего облучения кристалла и без него. Предложен метод использования эффекта для формирования временной метки взаимодействия ионизирующего излучения с сцинтиллятором.

Спектрально-кинетические свойства нестационарного поглощения гибридных наноструктур серебро–фталоцианин меди

In this paper, we studied the dynamics of transient absorption spectra of a hybrid nanostructure (Ag–CuPc)6 Ag based on island silver films and copper phthalocyanine thin films, as well as individual structural units of this system, by femtosecond transient absorption spectroscopy. It is found that the effects observed for a hybrid nanostructure reflect the existing mutual influence of the plasmonic and organic subsystems on the spectral-kinetic characteristics of each other. The characteristic time of the main component of induced optical density kinetics at a wavelength λ = 525 nm (τ ~ 15 ps) that is caused by singlet-triplet relaxation of the excited electronic states of the organic subsystem of the hybrid structure is noticeably shorter than the relaxation time (τ ~ 50 ps) at the same wavelength for a pure copper phthalocyanine film of 40 nm thickness, just the same as the total thickness of the organic subsystem in the hybrid structure. It is assumed that the presence of silver nanoparticles in the hybrid structure (Ag–CuPc)6 Ag, affects the probability of intersystem conversion in the organic subsystem, accelerating the transition of CuPc molecules to a long-lived triplet state due to a strong local field near the surface of the plasmon particle. The triplet-triplet absorption spectrum of copper phthalocyanine in the spectral range 470–750 nm was obtained.Представлены результаты исследования с фемтосекундным временным разрешением нестационарных спектров поглощения гибридных наноструктур на основе островковых пленок серебра и фталоцианина меди (CuPc). Установлено, что динамика нестационарных спектров поглощения гибридной системы (Ag–CuPc)6 Ag отражает существующее взаимное влияние плазмонной и органической подсистем на характеристики электронных состояний и спектрально-кинетические свойства друг друга. Время релаксации основной компоненты в кинетике релаксации наведенного поглощения на длине волны λ = 525 нм (τ ~ 15 пс), обусловленной синглет-триплетной релаксацией, для органической подсистемы CuPc суммарной толщиной l ~ 40 нм в гибридной структуре заметно короче времени релаксации (τ ~ 50 пс) аналогичной компоненты для чистой пленки фталоцианина меди такой же толщины. Предполагается, что присутствие наночастиц серебра в гибридной структуре (Ag–CuPc)6 Ag влияет на вероятность интеркомбинационных переходов в органической подсистеме, ускоряя переход молекул CuPc в долгоживущее триплетное состояние

ДИНАМИКА СВОБОДНЫХ НОСИТЕЛЕЙ В ТЯЖЕЛЫХ СКИНТИЛЯЦИОННЫХ МАТЕРИАЛАХ СО СТРУКТУРОЙ ГРАНАТА

Ce-doped Lu3 Al5 O12 (LuAG), and Gd3 Al2 Ga3 O12 (GAGG) crystals with and without codoping by Mg2+ ions have been studied by the nonlinear absorption spectroscopy method. A faster rise time of transient optical absorption has been observed in all crystals codoped with Mg in comparison to Mg-free samples. A significant difference in the time evolution of the differential optical density in GAGG in comparison to LuAG crystals is revealed. in gadolinium garnets an absorption band peaked in the blue-green range and decaying with characteristic time of ~2 ps is observed. This band is considered to be due to absorption of free electrons before their trapping by Ce3+doping ions. A broad transient absorption band in the yellowred region is attributed to absorption from the Ce3+ excited states. Легированные ионами Се кристаллы Lu3 Al5 O12 (LuAG) и Gd3 Al2 Ga3 O12 (GAGG) с и без кодопирования ионами Mg2+ исследованы методом нелинейной абсорбционной спектроскопии. Ускорение времени нарастания переходного оптического поглощения наблюдалось в кристаллах, кодопированных ионами Mg, по сравнению с образцами без Mg. Выявлено существенное различие во временной эволюции дифференциальной оптической плотности в GAGG в сравнении с кристаллом LuAG. В гадолиниевых гранатах наблюдается полоса поглощения в сине- зеленом диапазоне с затуханием с характерным временем ~2 пс. Эта полоса соотнесена поглощению свободными электронами до их захвата примесными ионами Ce3+. Широкая полоса переходного поглощения в желто-красной области обусловлена поглощением из возбужденных состояний ионов Ce3+.

СПЕКТРАЛЬНО-ВРЕМЕННАЯ ДИНАМИКА НЕСТАЦИОНАРНОГО ПОГЛОЩЕНИЯ МНОГОСЛОЙНЫХ ПЕРИОДИЧЕСКИХ ПЛАЗМОННЫХ НАНОСТРУКТУР

The features of the induced changes in the optical density spectra of multilayer Ag-Na3 AlF6 nanostructures under a femtosecond laser pulses exitation in the band of surface plasmonic resonance of absorption (SPRA) were studied. The dependence of the amplitude of the induced changes on the thickness of the dielectric Na3 AlF6 films separating the monolayeres of silver nanoparticles was registered. A significant increase of the optical response amplitude (up to 80 %) was found for the nanostructures with the quarter-wavelength Na3 AlF6 interlayers. For nanostructures with different-thickness dielectric Na3 AlF6 interlayers the characteristic relaxation times of induced changes at an excitation energy of 5–10 μJ do not practically vary, are equal to ~2 ps and coincide with the kinetic response time parameters of the used silver nanoparticle monolayers. Изучены особенности наведенных изменений в спектрах оптической плотности многослойных наноструктур Ag-Na3 AlF6 при их возбуждении фемтосекундными лазерными импульсами в полосе плазмонного поверхностного резонанса поглощения (ППРП). Зарегистрирована зависимость амплитуды наведенных изменений в области ППРП от толщины диэлектрических пленок Na3 AlF6 , разделяющих монослои наночастиц серебра. Обнаружено существенное увеличение амплитуды оптического отклика (до 80 %) для наноструктуры с четвертьволновыми прослойками Na3 AlF6 . Характеристические времена релаксации наводимых изменений при энергиях возбуждения 5–10 мкДж для наноструктур с различной толщиной диэлектрических прослоек Na3 AlF6 практически не изменяются, составляют ~2 пс и совпадают с временными параметрами кинетического отклика, характерными для используемого монослоя наночастиц Ag.

Psychological characteristics of Far North patients with arterial hypertension

Aim. To study psychological characteristics of arterial hypertension (AH) patients living in the Far North.Material and methods. In total, 203 individuals were examined: 153 patients (59 males, mean age 42,12+7,01 years; 94 females, mean age 51,39+4,07 years) with verified AH, as well as 50 persons without cardiovascular pathology (19 males, mean age 43,44+10,17 years; 31 females, mean age 37,37+9,59 years). Personality type and affective parameters were assessed using interviews, personality scales, and questionnaires.Results. The combination of hysteroid-hypochondriac and schizoid characteristics was a psychological AH marker in the Far North patients. Gender differences were related to affective sphere involvement in AH females. Behavioural traits in AH patients were characterized by problematic adaptation to changes in daily routine, low tolerance of unpredictable situations, pessimism, and exaggeration of expected threats.Conclusion. AH clinical course is determined by borderline psychological disorders, which points to a need for complex treatment, including behavioral and relaxation methods

Picosecond transient absorption rise time for ultrafast tagging of the interaction of ionizing radiation with scintillating crystals in high energy physics experiments

Here we report the first results of a search of a signature for picosecond time stamps of the interaction between ionizing particles and transparent crystalline media. The induced absorption with sub-picosecond rise time observed in a cerium fluoride scintillation single crystal under UV excitation is directly associated with the ionization of Ce(3+) atoms in CeF(3) crystals, and the very fast occurrence thereof can be used to generate picosecond-precise time stamps corresponding to the interaction of ionizing particles with the crystal in high energy physics experiments