Fluorescence Spectra Of Naphthalene Research Articles

Synchronous spectrofluorimetric determination of naphthalene in water samples using mixed micellar medium.

A mixed micellar medium of sodium dodecyl sulfate and Pluronic F-127 was used to enhance the fluorescence of naphthalene and to obtain lower LODs. The method was based upon measuring the first-derivative synchronous fluorescence spectrum of naphthalene by using a mixed micellar medium at a constant wavelength difference delta lambda = 60 nm, where a greater fluorescence enhancement was observed if compared to using a single surfactant separately. A linear fluorimetric calibration curve was obtained for naphthalene in a concentration range of 10-200 ng/mL. The LOD was 7.13 ng/mL, which is well below the health advisory limit for naphthalene in drinking water as suggested by the U.S. Environmental Protection Agency. The method can be easily adopted for determination of naphthalene in aqueous media including tap water and river water. The recoveries obtained were 95.979-115.645%. The proposed method was validated according to International Conference on Harmonization guidelines and successfully applied to determine naphthalene in real life water samples from different sources.

Comparative analysis of high-resolution spectra of naphthalene and its methyl-substituted derivatives cooled in a supersonic jet

We have carried out a comparative analysis of fine-structure fluorescence excitation and fluorescence spectra of naphthalene, 2,6-and 2,7-dimethylnaphthalene, and 2-methylnaphthalene molecules cooled in a supersonic jet. We have shown that both the frequencies and the intensities of most of the lines in the spectra of these molecules are correlated. Such a correlation facilitates interpretation of the spectra in the case when it is difficult to calculate the transition intensities and when lines corresponding to vibrations of different symmetry have close frequencies. For the considered molecules, a preliminary assignment of the lines in the fine-structure spectra is refined.

Measuring atmospheric naphthalene with laser-induced fluorescence

Abstract. A new method for measuring gas-phase naphthalene in the atmosphere is based on laser-induced fluorescence at low pressure. The fluorescence spectrum of naphthalene near 308 nm was identified. Naphthalene fluorescence quenching by N, O and HO was investigated in the laboratory. No significant quenching was found for HO with mixing ratio up to 2.5%. The quenching rate of naphthalene fluorescence is (1.980.18) 10cmmolecules for N, and (2.480.08)10cmmolecules for O at 297 K. Instrument calibrations were performed with a range of naphthalene mixing ratios between 5 and 80 parts per billion by volume (ppbv, 10. In the current instrument configuration, the detection limit is estimated to be about 20 parts per trillion by volume (pptv, 10 with 2 confidence and a 1-min integration time. Measurements of atmospheric naphthalene in three cities, Nashville, TN, Houston, TX, and New York City, NY, are presented. Good correlation between naphthalene and major anthropogenic pollutants is found.

Fluorescence of jet-cooled naphthalene: Emission spectra, lifetimes and quantum yields

Fluorescence spectra of naphthalene, C10H8, were obtained in the laboratory under conditions which provide an appropriate simulation of the cometary conditions: super-cooled gas phase molecules in a collision-free environment. Five spectra were recorded, the excitation energies ranging from 1422 to 5293 cm−1 above the first electronic state S1 at 32 020 cm−1. A comparison with previous jet-cooled naphthalene fluorescence spectra obtained by Beck et al. [1] and Hermine [2] shows that the former results are not consistent with the present ones. Spectra obtained by Beck et al. show weaker intensities at greater wavelengths compared to those obtained by Hermine and ourselves. We also measured the fluorescence lifetimes by recording the fluorescence decay as a function of time after the excitation of the molecules by monochromatic lasers and deduced the fluorescence quantum yields. A synthetic emission spectrum under solar irradiation is obtained for astrophysical implications.

Discrete electron-vibrational fluorescence spectrum of naphthalene vapor with selective resonance excitation

In this regard, investigations of the luminescence spectra of naphthalene and benzene in the gas phase are also of great interest because for these compounds the quasi-brightline structure of the spectra were obtained not only in frozen solutions, but also in the gas phase~ Below we shall consider literature data and discuss the obtained results of investigations of discrete fluorescence spectra of naphthalene in the gas phase.

CNDO/S calculations of resonance Raman spectra and pre-resonance excitation profiles of organic molecules.

The relative enhancement of the Raman intensities in the pre-resonance region has been computed for naphthalene, using the vibronic coupling expansion proposed by Albrecht. The relevant vibronic and transition moments have been computed in the CNDO/S approximation while the normal coordinates of naphthalene have been evaluated using a MINDO/3 program. The experimental pattern of intensities is reproduced in satisfactory way both for b 3g and a g vibrations. The most impo r tant states and the main vibronic terms in the expansion are individuated and d i scussed with respect to the vibronic borrowing present in the fluorescence spectrum of naphthalene. For styrene, the ature of the low-lying singlet states has been investigated through calculation of the resonance Raman spectrum and the pre-resonance Raman profiles of the three modes of CC stretching nature. A satisfactory agreement with the experiment is found and an analysis of the main contributions to the intensity is provided in terms of vibronic matrix elements. The possibility of destructive interference of diagonal and off-diagonal terms is analyzed for the three modes examined.

CNDO/S calculations of resonance raman spectra and pre-resonance excitation profiles of organic molecules.

The relative enhancement of the Raman intensities in the pre-resonance region has been computed for naphthalene, using the vibronic coupling expansion proposed by Albrecht. The relevant vibronic and transition moments have been computed in the CNDO/S approximation while the normal coordinates of naphthalene have been evaluated using a MINDO/3 program. The experimental pattern of intensities is reproduced in satisfactory way both for b 3g and a g vibrations. The most impo r tant states and the main vibronic terms in the expansion are individuated and d i scussed with respect to the vibronic borrowing present in the fluorescence spectrum of naphthalene. For styrene, the nature of the low-lying singlet states has been investigated through calculation of the resonance Raman spectrum and the pre-resonance Raman profiles of the three modes of CC stretching nature. A satisfactory agreement with the experiment is found and an analysis of the main contributions to the intensity is provided in terms of vibronic matrix elements. The possibility of destructive interference of diagonal and off-diagonal terms is analyzed for the three modes examined.

Vibronic coupling calculation of the pre-resonance Raman intensities of naphthalene

The relative enhancement of the Raman intensities in the pre-resonance region has been computed for naphthalene, using the vibronic coupling expansion proposed by Albrecht. The relevant vibronic and transition moments have been computed in the CNDO/S approximation, while the normal coordinates of naphthalene have been evaluated using a MINDO/3 program. The experimental pattern of intensities is reproduced in a satisfactory way both for b3g and ag vibrations. The most important states and the main vibronic terms in the expansion are individuated and discussed with respect to the vibronic borrowing present in the Fluorescence spectrum of naphthalene.

Features of fluorescence and absorption spectra of naphthalene and its deutero derivatives (under Shpol'skii-effect conditions)

The fluorescence and absorption spectra of naphthalene in different aggregate states have been investigat~ed on many occasions [1-5], but they cannot be regarded as fully interpreted. In an analysis of later experimental data, the Herzberg--Teller mechanism of vibronic interaction was introduced to explain the fluorescence spectrum of naphthalene [5]. An investigation of the intensity distribution [6] showed the absence of mirror symmetry between the fluorescence and absorption spectra in the region of the first electronic transition.

Excimer fluorescence spectra of aromatic liquids

The fluorescence spectra of naphthalene, pyrene, 1: 2-benzopyrene and the 2-methyl, 2-ethyl, 1,2-dimethyl, 1,6-dimethyl, 2,3-dimethyl and 2,6-dimethyl derivatives of naphthalene have been observed in the pure liquid state. Comparison with the solution spectra shows that each of the liquids has a large excimer emission component. From the temperature at which monomer emission becomes significant it is estimated that the ratio of the binding energies of the pyrene and naphthalene excimers is ⩾ 1·46.

On the fluorescence spectrum and decay time of naphthalene

The effect of temperature, solvent, concentration of solute and quenching by oxygen on the decay time and fluorescence spectrum of naphthalene was investigated. At high solute concentrations (>0·1 M) an anomaly in the emission spectrum is interpreted as being due to transient dimers, whereas at lower solute concentrations (<0·1 M), no evidence has been found to support the assumption of transient dimers. The decay time of naphthalene in paraffin oil when excited by a pulsed beam of electrons is unaccountably longer than that of naphthalene in a less viscous medium.

The fluorescence spectrum of naphthalene vapor in the 3100A region

The fluorescence spectra of naphthalene- h 8 and naphthalene- d 8 have been photographed in the 3100A region using a spectrograph with a resolution of about 0.5 cm −1. Three mercury lines in the region of 3125A were used for excitation and spectra were obtained at a pressure of ∼0.1 mm Hg (when emission occurs before many collisions between molecules have taken place) and with helium added to a pressure of 5 mm Hg (when vibrational deactivation takes place before emission). The low-pressure spectra are extensive and were used in making vibrational assignments. The high-pressure spectra are less extensive but contain further useful information: rotational contours in these spectra were used to support vibrational assignments. An understanding of the mechanism of the fluorescence has enabled an assignment of the 72cm −1 sequence interval to be made in both naphthalene- h 8 and - d 8. The contours of the 72cm −1 sequence members show evidence for Coriolis interaction in support of their assignments. The vibrations involved in some other sequences have been ascertained from the low-pressure spectra. Combination bands have been assigned which confirm the existence of the a g vibrations with frequencies of about 516 and 493 cm −1, respectively, in naphthalene- h 8 and - d 8.