Rotational temperatures in nonequilibrium free jet expansion of nitrogen

Coe, D.; Robben, F.; Talbot, L.; Cattolica, Robert J.

doi:10.1063/1.863041

Cited by 52 publications

(19 citation statements)

References 10 publications

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“…Muntz (31) and Coe et. al (32), using a theoretical treatment based on the Born approximation (valid at high E e ) which included only molecular angular momentum terms, have predicted electric dipole selection rules. However, the validity of such predictions for threshold EI which involves the motion of three highly correlated particles (an ion plus two near zero kinetic energy electrons) is highly questionable (33).…”

Section: Effects Of the Ionization Schemementioning

confidence: 99%

Non-Mass-Dependent Isotope Effects in the Formation of O₄⁺

Griffith

Gellene

1992

ACS Symposium Series

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Non-mass dependent isotopic enrichment of 17 O and 18 O has been observed mass spectrometrically in O4+ ions produced by termolecular association reactions of O2+ and O2 where the O2+ was generated by electron ionization of O2. The enhancement is strongly dependent on the energy of the ionizing electrons, decreasing from a near ten-fold enhancement at threshold for O2+ production to no enhancement above 40 eV. Additionally, O2+ generated near threshold was found to be significantly less efficient in producing O4+ than O2+ ions generated at higher energies. A permutation inversion symmetry analysis of the termolecular association reaction suggests that the results can be understood in terms of a symmetry restriction on the O2+( 2 Π g ) rotational states which can efficiently access the electronic ground state of O4+ upon collisions with O2. The restriction is rooted in the Pauli principle and vanishes when the O2+ ion is isotopically heteronuclear. The possible relevance of the non-mass dependent isotope enhancement in O4+ to similar enhancements found in stratospheric and laboratory -produced ozone is discussed.Motivated by relevance to interstellar and upper atmosphere chemistry, termolecular association reactions producing O4 have been the subject of experimental and theoretical investigations for almost thirty years. In 1963, Curran (7) investigated the effect of O2 pressure and ionizing electron energy on the rate of O4 production and found the results to be consistent with the two step mechanism:02 + e--» O2 +2e-(la)Surprisingly, the appearance potential of O4 was found to be 16.9±0.1 eV, almost 5 eV greater than that of ground state O2. On the basis of this observation Curran

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Section: Effects Of the Ionization Schemementioning

confidence: 99%

Non-Mass-Dependent Isotope Effects in the Formation of O₄⁺

Griffith

Gellene

1992

ACS Symposium Series

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“…A numerical calculation shows, that full width at half maximum of the distribution (9) lies in the limits from 0,48Jmax tO I ,64Jmax, and spectral width may be estimated, using expressions (3)(4)(5) and ( 42 cm-' Fig.3 The benzene ionizing spectra.…”

Section: Appendixmentioning

confidence: 99%

“…This method is the basic in the relaxation processes investigations at the supersonic beames formation, and low-atom molecules, mainly N2, are used [1][2][3][4]. It is believed such found rotative temperature data are close to the axial translative temperature -one ofthe main gasdinamic stream characteristics [5].…”

Section: Introductionmentioning

confidence: 99%

Vibrationally excited benzene molecular cooling in supersonic beams

1998

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There were examined photoionization spectra ofbenzene cooled in supersonic molecular beams. Compounds of benzene vapor with several buffer gases were used -He, Ne, Ar, Kr, N2, CH4. The photolonization was performed by frequency tuning KrF laser (linewidt 0.8 cm1; tuning range 120 cm-').The process is step-by-step, with the real intermediate level. The tuning range envelops two vibronic bands 6o lo 16,' and 6,I los, belonging to electron transition 'Aig Bu. The ionization spectrum is mainly depend on the absorption spectrum at the first step. The both bands are hot, but nevertheless the ionization efficiensy at supersonic beam conditions is rather high; it's caused by large "gap" of vibronic temperature from rotational and translative ones.As it was experimentally defined with various buffer gases, that bands intensity relation varies too. This fact testify about vibronic cooling dependence on the sort of buffer.Besids, a significant difference in the bands envelope contour widths was discovered. That is rather unusual fact, as the band width mainly depends on rotative temperature in the low state ( rotative band structure wasn't resolved in that experiments). Based on there data the rotative temperature estimation shows for benzene, that rotative temperature of molecules with excited 6th vibronic mode is always lower ( 4.5K with Ne buffer), than molecules with I 6t one ( I 5 K at the same conditions). This fact was interpreted as the rotationall-vibronic interaction result.As degenerated 6t mode has vibrational angular momentum, which is absent in the 16th, degenerated as well, so rotative-vibronic interaction in the first case s significantly stronge, and leads to levels splitting coparable with the rotative structure As the result rotative levels density for 6t mode twice more.The interraption moment for rotative relaxation, i.e the time, or characteristic distance from the nozzle cut-off, where rotative relaxation in the molecular beam forming on translative temperature and molecular density as well as sublevels encrg interval. The last is twice less for molecula with the excited 6 mode, that is the reasopn of the,r more intense rotative cooling.

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“…Although the rotational distribution shows nonlinearity in the Boltzmann plot, he described in his paper that the nonlinearity was caused by secondary electrons. On the contrary, Coe et al [5] proposed a new analytical model including a quadrupole interaction with an ejected electron as well as a dipole interaction with a primary electron and reduced the spectroscopic data to the Boltzmann distribution successfully, concluding that there were no deviation from the Boltzmann distribution in the rotational states in wider range of P 0 D from 15.9 to 1016 Torr-mm. Only recently, the quantum mechanics has been introduced to numerical simulations and the non-Boltzmann distribution in the rotational levels has been discussed actively.…”

Section: Introductionmentioning

confidence: 95%

“…Unfortunately, he was still comparing the simulation data with Marrone's results, which are the only experimental data for researchers studying the rotational relaxation. Because there have been no experimental data of the rotational energy distributions since the experiments by Marrone [4] and Coe et al [5], we desire the precise experimental data earnestly using the laser spectroscopy.…”

Section: Introductionmentioning

confidence: 99%