High resolution absorption cross-section measurements of N2O at 295–299 K in the wavelength region 170–222 nm

Yoshino, K.; Freeman, D. E.; Parkinson, W. H.

doi:10.1016/0032-0633(84)90065-5

Cited by 33 publications

(36 citation statements)

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“…Thus, sufficient degrees of ) Umemoto (1999) weighted linear fit: − − − this paper VUV spectroscopy:  Selwyn and Johnston (1981), 301 K ZPE theory:  σ (Yoshino et al (1984)), 0.0006 nm resolution  σ (Yoshino et al (1984)), 0.5 nm adjacent average  σ (Mérienne et al (1990)), polynomial fit  σ (Selwyn et al (1977) conversion were achieved within reasonable irradiation time (extending up to 22 and 33 h, respectively), and the fractionation constants derived from Rayleigh plots have small errors (Table 2). …”

Section: Photolysis With Broadband Light Sourcesmentioning

confidence: 96%

“…The corresponding spectral photolysis rates (Fig. 2) were calculated from direct measurements of the emission spectra of the Sb (Röckmann et al, 2001) and Hg/Xe lamps (Saueressig, 1999), convoluted (where appropriate) with transmission spectra of four interference filters (Melles Griot) and the N 2 O absorption spectrum at room temperature (Selwyn et al, 1977;Yoshino et al, 1984). The emission spectrum of the D 2 lamp was not measured directly, but was calculated from measurements of the spectral radiant intensity of a D 2 calibration lamp (Mathias Richter, personal communication, 2001), transmission functions of synthetic silica windows (Hamamatsu) and high-resolution O 2 absorption cross sections (Minschwaner et al, 1992).…”

Section: Photolysis With Broadband Light Sourcesmentioning

confidence: 99%

“…The fractionation constants predicted by the zero point energy (ZPE) theory (Miller and Yung, 2000;Yung and Miller, 1997) have been derived by blue-shifting the high resolution absorption spectrum of Yoshino et al (1984) in addition to the polynomial approximations of ln σ proposed by Selwyn et al (1977) and Mérienne et al (1990), assuming that these spectra represent essentially the absorption cross section of the most abundant N 2 O species, 14 N 2 16 O. Although the relative order of 18 O and position-dependent 15 N fractionations is predicted correctly, their magnitudes are about a factor of 2 too low.…”

Section: Synoptic View Of the Wavelength Dependencementioning

confidence: 99%

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Wavelength dependence of isotope fractionation in N<sub>2</sub>O photolysis

et al. 2003

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Abstract. In previous reports on isotopic fractionation in the ultraviolet photolysis of nitrous oxide (N 2 O) only enrichments of heavy isotopes in the remaining N 2 O fraction have been found. However, most direct photolysis experiments have been performed at wavelengths far from the absorption maximum at 182 nm. Here we present high-precision measurements of the 15 N and 18 O fractionation constants (ε) in photolysis at 185 nm. Small, but statistically robust depletions of heavy isotopes for the terminal atoms in the linear N 2 O molecule are found. This means that the absorption cross sections σ ( 15 N 14 N 16 O) and σ ( 14 N 2 18 O) are larger than σ ( 14 N 2 16 O) at this specific wavelength. In contrast, the central N atom becomes enriched in 15 N. The corresponding fractionation constants (±1 standard deviation) areTo our knowledge, this is the first documented case of such a heavy isotope depletion in the photolysis of N 2 O which supports theoretical models and pioneering vacuum ultraviolet spectroscopic measurements of 15 N substituted N 2 O species that predict fluctuations of ε around zero in this spectral region (Selwyn and Johnston, 1981). Such a variability in isotopic fractionation could have consequences for atmospheric models of N 2 O isotopes since actinic flux varies also strongly over narrow wavelength regions between 175 and 200 nm due to the Schumann-Runge bands of oxygen. However, the spacing between maxima and minima of the fractionation constants and of the actinic flux differ by two orders of magnitude in the wavelength domain. The wavelength dependence of fractionation constants in N 2 O photolysis can thus be approximated by a linear fit with negligible consequences on the actual value of the spectrally averaged fractionation constant. In order to establish this linear fit,Correspondence to: J. Kaiser (kaiser@princeton.edu) additional measurements at wavelengths other than 185 nm were made using broadband light sources, namely D 2 , Hg/Xe and Sb lamps. The latter lamp was used in conjunction with various interference filters to shift the peak photolysis rate to longer wavelengths. From these experiments and existing data in the literature, a comprehensive picture of the wavelength dependence of N 2 O photolysis near room-temperature is created.

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Section: Photolysis With Broadband Light Sourcesmentioning

confidence: 96%

Section: Photolysis With Broadband Light Sourcesmentioning

confidence: 99%

Section: Synoptic View Of the Wavelength Dependencementioning

confidence: 99%

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Wavelength dependence of isotope fractionation in N<sub>2</sub>O photolysis

et al. 2003

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“…The absorption spectrum 5,6 has a broad Gaussian shape, reflecting a primarily direct fragmentation, with very weak vibrational structures due to temporary trapping of a tiny a) Electronic mail: johanalbrechtschmidt@gmail.com. b) Electronic mail: rschink@gwdg.de.…”

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confidence: 99%

Photodissociation of N2O: Energy partitioning

Schmidt

Lorenz²,

McBane

et al. 2011

The Journal of Chemical Physics

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The energy partitioning in the UV photodissociation of N 2 O is investigated by means of quantum mechanical wave packet and classical trajectory calculations using recently calculated potential energy surfaces. Vibrational excitation of N 2 is weak at the onset of the absorption spectrum, but becomes stronger with increasing photon energy. Since the NNO equilibrium angles in the ground and the excited state differ by about 70• , the molecule experiences an extraordinarily large torque during fragmentation producing N 2 in very high rotational states. The vibrational and rotational distributions obtained from the quantum mechanical and the classical calculations agree remarkably well. The shape of the rotational distributions is semi-quantitatively explained by a two-dimensional version of the reflection principle. The calculated rotational distribution for excitation with λ = 204 nm and the translational energy distribution for 193 nm agree well with experimental results, except for the tails of the experimental distributions corresponding to excitation of the highest rotational states. Inclusion of nonadiabatic transitions from the excited to the ground electronic state at relatively large N 2 -O separations, studied by trajectory surface hopping, improves the agreement at high j.

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“…The first absorption band ͑ ϳ 180 nm͒ is a broad Gaussian-type function with very weak diffuse vibrational structures superimposed to the background. 2,3 The structures indicate that some small fraction of the dissociating molecules is temporarily trapped near the Franck-Condon ͑FC͒ region. 4 Both the absolute magnitude and the intensity of the vibrational structures are temperature dependent 2 pointing to bending motion as the essential mode.…”

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confidence: 99%

Communication: Photodissociation of N2O—Frustrated NN bond breaking causes diffuse vibrational structures

Schinke

Suárez

Farantos

2010

The Journal of Chemical Physics

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The photodissociation of N2O is studied by wave packet calculations using a global three-dimensional potential energy surface for the first excited A1′ state. It is shown that the weak vibrational structures of the absorption cross section are caused by large-amplitude NN stretch motion, combined with strong excitation of the bend as well as the O–NN stretch. Weakening of the NN bond toward the N+NO channel is the necessary prerequisite.

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High resolution absorption cross-section measurements of N2O at 295–299 K in the wavelength region 170–222 nm

Cited by 33 publications

References 14 publications

Wavelength dependence of isotope fractionation in N<sub>2</sub>O photolysis

Wavelength dependence of isotope fractionation in N<sub>2</sub>O photolysis

Photodissociation of N2O: Energy partitioning

Communication: Photodissociation of N2O—Frustrated NN bond breaking causes diffuse vibrational structures

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High resolution absorption cross-section measurements of N2O at 295–299 K in the wavelength region 170–222 nm

Cited by 33 publications

References 14 publications

Wavelength dependence of isotope fractionation in N&lt;sub&gt;2&lt;/sub&gt;O photolysis

Wavelength dependence of isotope fractionation in N&lt;sub&gt;2&lt;/sub&gt;O photolysis

Photodissociation of N2O: Energy partitioning

Communication: Photodissociation of N2O—Frustrated NN bond breaking causes diffuse vibrational structures

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Wavelength dependence of isotope fractionation in N<sub>2</sub>O photolysis

Wavelength dependence of isotope fractionation in N<sub>2</sub>O photolysis