Oscillation, Rotation, and Spin Relaxation in NO

Bauer, Hans‐Jörg; Kneser, Hans O.; Sittig, Erhard

doi:10.1063/1.1730144

“…Thus it is found that the value of P,_0 for NO is 3.6 ? 0.4 X 10---at 300?K, in good agreement with the sound-propagation results of Bauer et al(17) and the extrapolated shock-wave results of Robof P,0_ for nitrogen is very small; it is calculated as 4 X 10-7 within an order of magnitude. Data for other gases, such as CO, CO and Kr, as quenching agents have been obtained by using them as coolant additives in a similar way; CO and CO2 give P,_o values of 0.25 X 10-4 and 1.7 X 10-4 respectively but krypton is totally without effect in quenching.By flashing with the photoflash alone it is possible to photograph the fluorescent emission progressions from v' latter case; but if the fluorescence levels is completely quenched by sufficient additive the (v -1) level is still observed to be over-populated in the ground state.…”

supporting

confidence: 89%

The Kinetics and Analysis of Very Fast Chemical Reactions

Norrish

¹

1965

Science

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The reactions about which I propose to speak are considered fast because they take place in times measured by microseconds and milliseconds. They comprise adiabatic processes such as explosive and pyrolytic reactions which themselves are made up of intermediate reactions involving transients of very short life, and also the isothermal reactions of atoms and radicals in both gaseous and liquid media. Reactions in this category, whose half-lives vary between 10-6 and 10-2 seconds, are not the fastest known processes: they are exceeded by ionic processes in solution, by the reactions of many electronically excited species and by the relaxation of rotational energy of molecules. They comprise, however, a very large class which until recently it had not been possible to follow kinetically or to analyse ob- 1470 The reactions about which I propose to speak are considered fast because they take place in times measured by microseconds and milliseconds. They comprise adiabatic processes such as explosive and pyrolytic reactions which themselves are made up of intermediate reactions involving transients of very short life, and also the isothermal reactions of atoms and radicals in both gaseous and liquid media. Reactions in this category, whose half-lives vary between 10-6 and 10-2 seconds, are not the fastest known processes: they are exceeded by ionic processes in solution, by the reactions of many electronically excited species and by the relaxation of rotational energy of molecules. They comprise, however, a very large class which until recently it had not been possible to follow kinetically or to analyse ob-1470 jectively. Very much had indeed been achieved by the study of the overall kinetics and stoichiometry of explosive and photochemical processes, and the various patterns of chain reactions and radical reactions which have emerged constitute an impressive inductive achievement. That the new methods of kinetic spectroscopy have confirmed in no small measure the modern deductions from reaction theory is satisfactory, but I hope to show here that they have also contributed much in their own right, and have elucidated mechanisms of chain reactions, radical processes and relaxation phenomena which were hitherto obscure.The methods of flash photolysis and kinetic spectroscopy which were discovered in our laboratory at Cambridge and developed in the beginning by Porter jectively. Very much had indeed been achieved by the study of the overall kinetics and stoichiometry of explosive and photochemical processes, and the various patterns of chain reactions and radical reactions which have emerged constitute an impressive inductive achievement. That the new methods of kinetic spectroscopy have confirmed in no small measure the modern deductions from reaction theory is satisfactory, but I hope to show here that they have also contributed much in their own right, and have elucidated mechanisms of chain reactions, radical processes and relaxation phenomena which were hitherto obscure.The methods of flash photolysis and kinet...

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“…The errors from photometry of the absorption spectra show that these data are accurate to about ± 10 % (the origin of these and other inaccuracies is now understood and more accurate results should be obtainable). The reciprocal relaxation time can be split into two terms k3 = *4(NO) + *5(N 2) thus yielding a value for P10 for NO of 3-6 + 0-4 x 10~4 (in excellent agreement with sound absorption (Bauer et al 1959) and the extrapolated shock wave results (Robben 1959)) and P1_0 for N2 of 4 x 1 0 7, the latter quantity being accurate to within an order of magnitude.…”

Section: Quantum Yield and Temperature Risementioning

confidence: 54%

“…The relaxation time in Kr + NO mixtures depended only on the partial pressure of NO and the temperature. Relaxation of vibration and spin orbit coupling has recently been described by Bauer, Kneser & Sittig (1959) measured by sound absorption; they recorded P01 = 3-8 x 10-4 at 20 °C and spin orbit relaxation occurred once in sixteen collisions.…”

mentioning

confidence: 94%

Fluorescence and vibrational relaxation of nitric oxide studied by kinetic spectroscopy

Basco

¹

,

Callear

²

,

Norrish

³

1961

Proc. R. Soc. Lond. A

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The first excited vibrational level of the ground electronic states of nitric oxide was populated above its equilibrium value by flash photolysis of nitric oxide + inert gas mixtures, under isothermal conditions. Electronic excitation NO 2 II ( v = 0) + hv → NO 2 Ʃ ( v = 0, 1, 2) was followed either by fluorescence NO 2 Ʃ ( v = 0, 1, 2) → NO 2 II ( v = 0, 1, 2...) + hv , or by quenching NO 2 Ʃ ( v = 0, 1, 2) + M → NO 2 II( v = 0, 1, 2...) + M , causing a non-equilibrium population of the vibrational levels of the ground electronic states. Subsequently, the reactions NO 2 II ( v = 1) + M → NO 2 II ( v = 0) + M and NO 2 II ( v = 1) + NO 2 II ( v = 0) → 2NO 2 II ( v = 1) caused a decay of the vibrationally excited molecules with time; this was followed in absorption by kinetic spectroscopy. Because of the rapidity of the last reaction, bands of NO2 II with v >1 were usually observed only in the fluorescence spectrum. In mixtures of 1 to 5 mm of NO with a large excess of nitrogen or krypton, the concentration of NO2 II ( v = 1) produced by the flash was of the order of 10-1 mm pressure, i. e. about the same concentration which is present in one atmosphere pressure of NO at room temperature. The absolute concentration of NO2 II ( v = 1) was measured accurately by plate photometry, high pressures of NO being used for calibration. The recorded probabilities of vibrational relaxation, P1-0, for NO2 II ( v = 1), and radii for electronic quenching, σ e , by NO, N 2 , CO, H 2 O and CO 2 , are P 1-0 σ e (Å) NO 3.55 x 10 -4 14 N 2 4 x 10 -7 ≤ 2x 10 -2 CO 2.5 x 10 -5 0.6 H 2 O 7 x 10 -3 30 CO 2 1.7 x 10 -4 5 With the use of an analytic form for the flash duration, the entire rise and fall of the concentration of excited species was quantitatively interpreted. A very small fraction of the NO was decomposed by the flash, due either to absorption of radiation below 1900 Å or by reaction of metastable NO molecules with each other or with ground state molecules. Abnormal effects were observed in NO+ H 2 +inert gas mixtures and chemical reaction occurred.

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“…This is similar to Fig. I except that 0, has replaced H 2 0 , and all the arrows [17] to [27] indicating previous reaction paths have been omitted in Fig. 2 for clarity.…”

mentioning

confidence: 60%

“…For NO the V + T process has been studied over a wide temperature range for M = Ar and NO (26)(27)(28)(29)(30)(31)(32)(33)(34)(35)(36)(37)(38). For M = H,O, CO,, N,, and CO there are only measurements at 300 "K (28).…”

Section: Comentioning

confidence: 99%

Energy Transfer Processes in the Stratosphere

Taylor¹

1974

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During the past clecacle or two considerable fundamental information has been acquired on the mechanisms and rates of molecular energy transfer among vibrational, rotational, and electronic states. It is a well-known fact that the rate and even the products of a chemical reaction can be n~arltedly influenced by the degree of internal state excitation of the reactants. Also, it is clear that many of the chemical processes o c c~~r r i n g in the upper atmosphere produce atoms or n~olecules in excited states. I t will be the purpose of this paper to review the state of knowledge of energy transfer nlechanisn~s and kinetic rates as it pertains to atmospheric constituents and to attempt to indicate possible important roles of energy, transfer in the physics and chemistry of the stratosphere. Some specific examples will rnclude vibrational relaxation of OH a n d On, the possible role of atomic species as quenchants, and electronic/vibrational energy transfer processes.ALI cours des deus dernitres cltcennies, de l'information fonclamentale considtrable a 6tc acquise sur les micanismes et les vitesse de transfert d'tnergie mol6culaire entre les ttats vibrationnels, rotationnels et Clectroniq~~es. C'est un fait bien connu que la vitesse et m&me les produits d'tlne rCaction chimique peuvent &tre profondtment influences par le degrt d'activation de l'itat interne des I-tactifs. Aussi, est-il clair que plusieurs cles processus chinriques survenant dans la haute atn1osphkr:e produisent cles atonles o u des moltcules aux ttats excitts. 11 sera du but de cette p~~blication de donner un cornpte rendu sur les connaissances des mtcanismes et des vitesses cinttiqlles de transfert d'tnergie conlme il apparlient aux constit~~ants atmosphtriq~~es et de tenter cl'indiquer des r6les importants possibles de transfert d'tnergie dans la physique et la chimie de la stratosphkre. Quelques exemples prtcis comprenclront une relaxation vibrationnelle de OH el O:,, le r61e possible d'esptces a t o m i q~~e s comme inhibiteurs et cles processus de transfer1 d'inergie tlectronique/vibrationnelle.[Traduit par le journal]Can.

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Oscillation, Rotation, and Spin Relaxation in NO

Cited by 56 publications

References 1 publication

The Kinetics and Analysis of Very Fast Chemical Reactions

The Kinetics and Analysis of Very Fast Chemical Reactions

Fluorescence and vibrational relaxation of nitric oxide studied by kinetic spectroscopy

Energy Transfer Processes in the Stratosphere

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