Production of electronically excited iodine atoms I(5p52P12) by collisional release in molecular I2

The appearance rate of 1^* (5p⁵²P_{$\text{1}\text{2}$}) following laser photolysis of molecular I₂ 1.2 kT below the dissociation limit o the I₂ (B³ Π_ou+) state has been monitored by time-resolved atomic absorption as a function of I₂ pressure. Data were also taken with N₂ as an added gas. The results confirm the production of I^* from the B state by a collisional process and reveal an additional process by which I^* continues to appear for several hundred nanoseconds after the laser pulse even at N₂ pressures as high as 750 torr.     

Infrared multiple-photon dissociation of N2H4 and CH3NH2 fluence dependence of the production of NH2

The multiple-photon dissociation of N₂H₄ and CH₃NH₂ by pulsed CO₂ laser light to produce NH₂(X?²B_I has been studied using the laser-induced fluorescence detection method. The relative NH₂ yield, represented by the fluorescence signal, has been measured as a function of the fluence from the threshold at about 0.1 J/cm² to about 100 J/cm², at different CO₂-laser lines and at pressures down to 10^?4 Torr.     

Electronic to vibrational energy transfer and relaxation in matrices. II. Hg in mixed N2/Kr matrices

The electronic fluorescence spectrum of Hg-doped N₂/Kr mixed matrices obtained by laser excitation of the Hg³P₁ level is composed of the Hg “atomic” (³P₁—¹S₀ and ³P₀—¹S₀) fluorescence and the exciplex fluorescence due to the (Hg—N₂)^* complex stable in the excited state. The temperature dependence of their intensities and lifetimes was studied in the temperature range 12–24 K. It is argued that the essential part of the ³P₀ and exciplex emission is due to two types of Hg sites with one N₂ nearest neighbor, differing probably in the orientation of the N₂ molecular axis. Strong irreversible effects due to the diffusion of N₂ molecules induced by laser irradiation are observed.     

Differential cross sections for fine-structure inelastic collisions of K(42P) with Ar,Kr and N2

We report measurements of differential cross sections for fine-structure inelastic collisions of potassium (4²P_3/2-4²P_1/2 with Ar, Kr and N₂. The experiment uses crossed molecular beams and a method to detect scattering angles by the analysis of Doppler shifts in laser induced fluorescence. The experimental results for KAr are compared with calculations.     

Infrared multiphoton dissociation of DN3 and HN3: Formation and reaction of electronically excited ND

Chemiluminescence is observed from DN₃ at pressures below 100 mtorr following irradiation with the focused output of a CO₂ TEA laser. Emission is attributed to ND₂(²A_I) formed in the reaction ND(a¹Δ) + DN₃ → ND₂ (²A₁) + N₃. The ND(a¹Δ) is produced in the primary photolysis. Time resolved studies of the fluorescence permit determination of the rate constant for the chemiluminescent reaction (2.09 ± 0.31 μs^?1 torr^?1). Multiphoton dissociation of HN₃ by use of a laser wavelength coincident with a hot band absorption is also demonstrated.     

Optical spectroscopy of low-phonon Ho3+ doped BaY2F8 single crystal

The Ho:BaY₂F₈ crystal was grown by Czochralski method. The crystal phase structure and absorption spectra were tested, the absorption peak exists near 899 nm, the absorption cross section was 1.27 × 10^?21 cm². The emission spectra of crystals in the vicinity of 2 and 3.9 μm were measured, the 2 μm near infrared light induced by ⁵I₇ → ⁵I₈ transition of Ho3+ ions was observed, as well as the fluorescence output at 3.9 μm (⁵I₅ → ⁵I₆), emission cross section at 3.9 μm was calculated to be 0.86 × 10^?21 cm². We suppose that the Ho:BaY₂F₈ crystal has a large application prospect for the 2–4 μm wavelength near infrared laser.     

Ar+ laser-induced fluorescence in NO2

The assignment of the resonant fluorescence induced by the AR⁺ laser lines in ¹⁴N¹⁶O₂ is reported for the first time with the 4727 and 4765 Å laser lines and is further developed with the 4579 and 4965 Å laser lines.     

Rapid interspecies energy flow between vibrationally excited SF6 and the asymmetric stretch of N2O

Rapid, selective collision-dependent excitation of N₂O following pumping of SF₆ with a CO₂ laser is reported. The N₂O fluorescence rise depends on the pressure of each component and is dominated by the SF₆-dependent contribution of 2290 ms^?1 Torr^?1. The subsequent fall is governed by V→V processes among SF₆ vibrational modes.     

CH3O(X̄ 2E) production from 266 nm photolysis of methyl nitrite and reaction with NO

The CH₃O(X? ²E) radical produced by the 266 nm photolysis of CH₃ONO is characterized by laser induced fluorescence. Using a flowing gas cell the reaction rate of CH₃O(X? ²E) with NO is measured to be (2.08 ± 0.12) × 10^?11 cm³ s^?1 based upon disappearance of CH₃O and appearance of HNO detected by laser induced fluorescence. Upper limits for CH₃O reactions with CH₄, CO, N₂O, NH₃, CH₃OH, (CH₃)₃CH and CH₂CHCH₂CH₃ are reported. These reactions are all too slow to measure under our experimental conditions.     

127I Mössbauer spectra for phenyliodonium ylides

¹²⁷I Mössbauer spectra for the phenyliodonium ylides were measured at 20 K. The valence electron populations (N_s, N_x-z) and the charge number (Z_I) for iodine atom are estimated from the Mössbauer parameters. The obtained populations were very close to those of diphenyliodonium chloride having two I-C primary bonds. To examine the possibility of some double bond character, the electron populations for the case of N_z = 1.90 are estimated. In this case, the Z_I values become larger as 1.2-1.3, and these values were unreasonably large because the values are close to those of PhICl₂, PhI(OAc)₂ having electron withdrawing ligands. Thereby, ¹²⁷I Mössbauer parameters suggest little double bond character for phenyliodonium ylides.     

Temperature dependence of the vibration-vibration transfer rates from CO2 and N2O excited in the (0001) vibrational level to 14N2 and 15N2 molecules

V-V transfer rates from CO₂ and N₂O excited in the (00⁰1) vibrational level to ¹⁴N₂ and ¹⁵N₂ are determined from 150 to 1200 K using the laser fluorescence method, and compared with values calculated on the basis of dipole-quadrupole interactions.     

Lifetime and collisional depopulation of the metastable 5D 3/2-state of Yb+

The lifetime and collisional depopulation rates of the metastable 5D _3/2 state of Yb⁺ have been determined in a radiofrequency ion trap by observation of the fluorescence count rate after ion excitation by a short laser pulse. From measurements using He, N₂ and H₂ as buffer gases between 10^?8 and 10^?6 mbar pressure and linear extrapolation to zero pressure we obtain a lifetime of τ=52.15±1.00 ms and rate constants ofR(H₂)=(1.02±0.10)×10^?9 cm³/s andR(N₂)=(1.78±0.19)×10^?10 cm³/s. The lifetime is in fair agreement with a calculated value of 74 ms.     

Measurement of the rotational energy distribution of ground state N+2 ions from H+2N2 collisions by laser-induced fluorescence

The rotational energy distribution of ground state N⁺₂ ions produced by interaction of a principally H⁺₂ ion beam with N₂ has been measured at projectile ion energies of 10 and 2.5 keV by observation of the laser induced fluorescence in the N⁺₂ first negative system (0, 0) band. At 10 keV, the rotational energy distribution is Boltzmann (432 K), due to heating of the gas by the intense ion beam. At 2.5 keV, rotational excitation is definitely observed.     

Origin of InI emission in laser studies of the crossed beam reaction In+I2

When a beam of In is cross fired at a beam of I₂ and the intersection is irradiated by various cw laser sources, InI emission is observed. The origin of this emission is shown to be laser-induced fluorescence (LIF) from the ground state indium monoiodide product of the reaction In + I₂ → InI + I, rather than laser-induced chemiluminescence (LIC) through the excitation of the I₂ reagent in the reaction In + I₂³ → InI* + I. An upper bound on the cross section for the later process is estimated to be ?2.5 × 10^?16 cm². The LIF excitation spectrum reveals a strong inversion in the InI vibrational population distribution, with the fraction of the total excess energy of reaction in vibration exceeding 0.5. Preliminary results for the Tl + I₂ reaction system show the same LIF m     

The mechanism of nitrogen fluorescence inside a femtosecond laser filament in air

The visible and near-UV fluorescence spectroscopy of air generated inside a femtosecond laser plasma filament was studied. The primary reactions, , populates the electronic excited state N₂(C³П_u) of N₂. The N₂ fluorescence is not by direct electron–ion recombination of . Using a pump–probe method, the fluorescence lifetime of C³П_u of N₂ at atmospheric pressure was determined to be about 85 ps.     

A Deadly Organometallic Luminescent Probe: Anticancer Activity of a ReI Bisquinoline Complex

The photophysical properties of [Re(CO)₃(L ‐N₃)]Br (L ‐N₃=2‐azido‐N,N‐bis[(quinolin‐2‐yl)methyl]ethanamine), which could not be localized in cancer cells by fluorescence microscopy, have been revisited in order to evaluate its use as a luminescent probe in a biological environment. The Re^I complex displays concentration‐dependent residual fluorescence besides the expected phosphorescence, and the nature of the emitting excited states have been evaluated by DFT and time‐dependent (TD) DFT methods. The results show that fluorescence occurs from a ¹LC/MLCT state, whereas phosphorescence mainly stems from a ³LC state, in contrast to previous assignments. We found that our luminescent probe, [Re(CO)₃(L ‐N₃)]Br, exhibits an interesting cytotoxic activity in the low micromolar range in various cancer cell lines. Several biochemical assays were performed to unveil the cytotoxic mechanism of the organometallic Re^I bisquinoline complex. [Re(CO)₃(L ‐N₃)]Br was found to be stable in human plasma indicating that [Re(CO)₃(L ‐N₃)]Br itself and not a decomposition product is responsible for the observed cytotoxicity. Addition of [Re(CO)₃(L ‐N₃)]Br to MCF‐7 breast cancer cells grown on a biosensor chip micro‐bioreactor immediately led to reduced cellular respiration and increased glycolysis, indicating a large shift in cellular metabolism and inhibition of mitochondrial activity. Further analysis of respiration of isolated mitochondria clearly showed that mitochondrial respiratory activity was a direct target of [Re(CO)₃(L ‐N₃)]Br and involved two modes of action, namely increased respiration at lower concentrations, potentially through increased proton transport through the inner mitochondrial membrane, and efficient blocking of respiration at higher concentrations. Thus, we believe that the direct targeting of mitochondria in cells by [Re(CO)₃(L ‐N₃)]Br is responsible for the anticancer activity.     

Vibrational energy transfer from the υ = 1 level of carbon monoxide to the υ = 1 level of the two isotopic species of nitrogen: 14N2 and 15N2

V-V transfer rates from CO (υ = 1) to ¹⁴N₂ and ¹⁵N₂ are determined from 100 to 700 K using the laser fluorescence method. The great effect of the energy level gap between the colliding partners is dramatically demonstrated. Theoretical considerations explain the observed difference.     

N2O5 photolysis products investigated by fluorescence and optoacoustic techniques

Pulsed laser photolysis of N₂O₅ near 290 nm coupled with fluorescence detection (calibrated by NO₂ photolysis) showed that the O(³P) quantum yield is ≤0.1. A pulsed laser optoacoustic technique in a flow tube (ca. 6 torr of N₂) was tested by photolysis of NO₂ and then applied to N₂O₅. Nitric oxide was added to react with NO₃ free radical and the resulting increase in the optoacoustic signal confirmed the presence of NO₃ free radicals. Based on the relative optoacoustic signals observed for NO₂ and N₂O₅, the quantum yield for NO₃ production is 0.8 ± 0.2.     

Synthesis and Nonlinear Optical Properties of a New A-π-A Two-Photon Compound Utilizing Dibenzothiophene as Center

A new two‐photon material, 3E,6E‐bis(2‐pyrid‐4′‐ylvinyl)dibenzothiophene (BPVDBT), has been firstly synthesized by an efficient Pd‐catalyzed Heck coupling route. The single‐ and two‐photon fluorescence, quantum yields, lifetimes, solvent effects of the chromophore were studied in detail and the compound exhibited solvent‐sensitivity. The fluorescence intensity (I_out) and input excitation intensity (I_in) can fit in well with the quadratic parabolas, which indicates that the up‐converted fluorescence was induced by the two‐photon absorption (TPA). TPA cross‐section of BPVDBT has been measured using the two‐photon‐induced fluorescence method, whose value is 14.24×10^?50 cm⁴·s·photon^?1·molecule^?1 at 750 nm. The experimental results confirm that BPVDBT is a good two‐photon absorbing chromophore with an A‐π‐A type.     

Comparative performance of CF3I,CD3I and CH3I in an atomic iodine photodissociation laser

We have compared the performance of CF₃I, CD₃I, and CH₃I in an atomic iodine photodissociation laser over the pressure range 1–200 torr. At pressures below 5 torr, CD₃I produces larger energy outputs, while above 5 torr CF₃I gives superior performance. The crossing of the laser energy output versus pressure curves is explained on the basis of collisional quenching of I(²P_{$\text{1}\text{2}$})(≡I^*) by undissociated alkyl iodide.