Direct measurements of the rate constants for collisional removal of CHF<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mo>(</mml:mo><mml:mrow><mml:msup><mml:mover accent="true"><mml:mi>X</mml:mi><mml:mo>&#x02DC;</mml:mo></mml:mover><mml:mn>1</mml:mn></mml:msup><mml:msup><mml:mi>A</mml:mi><mml:mo>&#x2032;</mml:mo></mml:msup><mml:mrow><mml:mo>(</mml:mo><mml:mrow><mml:mn>0,1,0</mml:mn></mml:mrow><mml:mo>)</mml:mo></mml:mrow></mml:mrow><mml:mo>)</mml:mo></mml:mrow></mml:math> by argon (Ar), ethylene (C2H4), propene (C3H6), 1-butene (1-C4H8), iso-butene (i-C4H8), 1,3-butadiene (C4H6), are reported. CHF<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mo>(</mml:mo><mml:mrow><mml:msup><mml:mover accent="true"><mml:mi>X</mml:mi><mml:mo>&#x02DC;</mml:mo></mml:mover><mml:mn>1</mml:mn></mml:msup><mml:msup><mml:mi>A</mml:mi><mml:mo>&#x2032;</mml:mo></mml:msup><mml:mrow><mml:mo>(</mml:mo><mml:mrow><mml:mn>0,1,0</mml:mn></mml:mrow><mml:mo>)</mml:mo></mml:mrow></mml:mrow><mml:mo>)</mml:mo></mml:mrow></mml:math> was prepared by IRMPD of precursor CH2F2. Fluence independence removal rate constants by Ar, ethylene and propene are: 0.0045, 2.70 and 2.46 &#215; 10&#8722;11 cm3 molecule&#8722;1 s&#8722;1, faster than the rates for the vibrational ground state. 1,3-butadiene was measured at a fluence of 42Jcm&#8722;2, yielding a value of 0.81 &#215; 10&#8722;11 cm3 molecule&#8722;1 s&#8722;1. Iso-butene has fluence dependence removal rates, given 1.28 and 0.92 &#215; 10&#8722;11 cm3 molecule&#8722;1 s&#8722;1 for fluences of 50 and 32Jcm&#8722;2 respectively. For 1-butene a non-linear Stern-Volmer behaviour has been observed and attributed to fast resonant vibrational-to-vibrational (V-to-V) intermolecular energy transfer. The influence of this (V-to-V) energy transfer on the removal rates is discussed.

Jos&#233; A. Fern&#225;ndez

Alfredo Ortiz de Z&#225;rate

Mar&#237;a N. S&#225;nchez Rayo

Fernando  Casta&#241;o

Direct Measurements of Removal Rates of CHF<svg style="vertical-align:-2.3205pt" height="26.025" version="1.1" viewBox="0 0 97.962502 26.025" width="97.962502" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg"><g transform="matrix(.017,-0,0,-.017,.062,23.075)"><path id="x28" d="M300 -147l-18 -23q-106 71 -159 185.5t-53 254.5v1q0 139 53 252.5t159 186.5l18 -24q-74 -62 -115.5 -173.5t-41.5 -242.5q0 -130 41.5 -242.5t115.5 -174.5z" /></g><g transform="matrix(.012,-0,0,-.012,9.187,9.812)"><path id="x223C" d="M548 311q-21 -57 -59 -94t-89 -37q-53 0 -128 52q-55 38 -84 38q-39 0 -70.5 -23t-45.5 -60l-32 12q21 57 59 94t89 37q53 0 128 -52q55 -38 84 -38q39 0 70.5 23t45.5 60z" /></g><g transform="matrix(.017,-0,0,-.017,5.95,24.262)"><path id="x1D44B" d="M775 650l-6 -28q-60 -6 -81.5 -16t-61.5 -54l-175 -191l125 -243q30 -58 48.5 -71t82.5 -19l-5 -28h-275l7 28l35 4q31 4 37 12t-6 34l-108 216q-140 -165 -177 -219q-16 -22 -10.5 -30.5t41.5 -13.5l22 -3l-7 -28h-244l8 28q52 4 75 15.5t67 52.5q48 46 206 231&#xA;l-110 215q-26 51 -44 63t-72 17l6 28h250l-6 -28l-27 -4q-30 -5 -35 -10t3 -27q17 -43 95 -190q70 78 154 185q15 21 10 29.5t-33 12.5l-30 4l5 28h236z" /></g><g transform="matrix(.012,-0,0,-.012,19.412,7.613)"><path id="x31" d="M384 0h-275v27q67 5 81.5 18.5t14.5 68.5v385q0 38 -7.5 47.5t-40.5 10.5l-48 2v24q85 15 178 52v-521q0 -55 14.5 -68.5t82.5 -18.5v-27z" /></g><g transform="matrix(.017,-0,0,-.017,25.738,23.075)"><path id="x1D434" d="M716 28l-8 -28h-254l8 28q55 5 66 17.5t5 47.5l-30 145h-232l-74 -138q-21 -43 -11 -54.5t72 -17.5l-6 -28h-235l8 28q53 7 73.5 21t53.5 70l319 540l33 8q6 -43 33 -176l80 -381q10 -49 26.5 -63t72.5 -19zM495 281l-49 264h-2l-149 -264h200z" /></g><g transform="matrix(.012,-0,0,-.012,38.2,14.912)"><path id="x2032" d="M227 744l-123 -338l-31 15l73 368q12 3 41.5 -8t36.5 -20z" /></g><g transform="matrix(.017,-0,0,-.017,42.362,23.075)"><use xlink:href="#x28"/></g><g transform="matrix(.017,-0,0,-.017,48.244,23.075)"><path id="x30" d="M241 635q53 0 94 -28.5t63.5 -76t33.5 -102.5t11 -116q0 -58 -11 -112.5t-34 -103.5t-63.5 -78.5t-94.5 -29.5t-95 28t-64.5 75t-34.5 102.5t-11 118.5q0 58 11.5 112.5t34.5 103t64.5 78t95.5 29.5zM238 602q-32 0 -55.5 -25t-35.5 -68t-17.5 -91t-5.5 -105&#xA;q0 -76 10 -138.5t37 -107.5t69 -45q32 0 55.5 25t35.5 68.5t17.5 91.5t5.5 105t-5.5 105.5t-18 92t-36 68t-56.5 24.5z" /></g><g transform="matrix(.017,-0,0,-.017,56.403,23.075)"><path id="x2C" d="M95 130q31 0 61 -30t30 -78q0 -53 -38 -87.5t-93 -51.5l-11 29q77 31 77 85q0 26 -17.5 43t-44.5 24q-4 0 -8.5 6.5t-4.5 17.5q0 18 15 30t34 12z" /></g><g transform="matrix(.017,-0,0,-.017,63.101,23.075)"><use xlink:href="#x31"/></g><g transform="matrix(.017,-0,0,-.017,71.26,23.075)"><use xlink:href="#x2C"/></g><g transform="matrix(.017,-0,0,-.017,77.975,23.075)"><use xlink:href="#x30"/></g><g transform="matrix(.017,-0,0,-.017,86.134,23.075)"><path id="x29" d="M275 270q0 -296 -211 -440l-19 23q75 62 116.5 174t41.5 243t-42 243t-116 173l19 24q211 -144 211 -440z" /></g><g transform="matrix(.017,-0,0,-.017,92.016,23.075)"><use xlink:href="#x29"/></g></svg> by Simple Alkenes

The role played by 6p metastable Xe level in the kinetics of discharge pumped XeCl laser emission is investigated by performing time resolved and time integrated fluorescence studies of the Xe 6p&#8211;6s emissions produced in the discharge plasma at various pressures of chlorine donor compounds. The results analyzed according to a simple kinetic model suggest that 6p level is populated through a cascading mechanism involving various Xe levels which is enhanced by the presence of the halogen donor compound. The laser emission dependence is also investigated as a function of the halogen donor pressure. The observations lead to the conclusion that 6p states do not play a relevant role in the formation of XeCl* molecules and that other Xe excited states should be considered to account for the participation of the neutral channel in the XeCl* formation mechanism.

M.  Castillejo

J. M. Figuera

I.  Garc&#237;a-Moreno

J. J. Medina

The Role of 6p States of X<small.letters>e</small.letters> in the Discharge Pumped X<small.letters>e</small.letters>C<small.letters>l</small.letters> Laser Emission

New NO laser emission from the photodissociation of BrNO has been observed between vib-rotational levels of the ground state of NO, using He and Br2 as buffer gases. Also, from the ClNO photodissociation several new NO vibro-rotational lines have been observed.The presence of a buffer gas was necessary to observe laser emission from BrNO and ClNO.The temporal behavior of the NO laser emission from the photodissociation of both nitrosyl halides has been studied.

J. I. Del Barrio Barrero

F. M. G.-Tablas

Chemical Lasers From the Photodissociation of Nitrosyl Halides

A new method for single shot velocity distribution measurement of metallic impurities of relevance for studies involving continuous sources, such as limiter experiments in fusion devises or sputtering experiments, based in the combination of Resonant Enhanced Multiphoton Ionization (REMPI) and Laser Induced Fluorescence (LIF) is proposed. High ionization yield and good time resolution are expected according to the numerical simulation of the experiment that has been run for several atomic species. Other possible applications of REMPI to plasma edge physics and to conventional techniques for velocity distribution measurements are briefly addressed.

F. L. Tabares

A New Technique for Ultrafast Velocity Distribution Measurements of Atomic Species by Post-Ionization Laser Induced Fluorescence (PILIF)

Different approaches are presented for the study of vibrational predissociation of triatomic van der Waals molecules. These methods are applied to the study of the He-I2 when I2 is excited to the B electronic state.The applicability of these methods is discussed in detail by comparing with &#x201C;exact&#x201D; quantum results.

G. Delgado-Barrio

S. Serna

S. Miret-Art&#xE9;s

O. Roncero

J. Campos-Mart&#xED;nez

P. Villarreal

Theoretical Approaches to Study the Vibrational Predissociation of Van Der Waals Molecules

Unimolecular multiphoton dissociation offers us a rather complete scheme where the transition from quantum mechanics to the classical regime can be experimentally followed. In the light of this idea, a new interpretation of the unimolecular multiphoton dissociation process is presented. The role that the intramolecular generation of instabilities and chaos may play in that process is discussed, both in single and double exposure experiments. Delayed double irradiation is also discussed and a criterion to define an effective single pulse notion in that kind of experiment is given.

P. F. Gonz&#225;lez-D&#237;az

M.  Santos

C. L. Sig&#252;enza

J. A. Torresano

New Directions in Multiphoton Dissociation

Absolute values of the total chemiluminescence cross-section for the beam-gas Ca(3P, 1D) + Cl4C &#8594; CaCl(A, B) + Cl3C and Ca(3P, 1D) + SF6 &#8594; CaF(A, B) + SF5 reactions have been measured at low collision energy, <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>E</mml:mi><mml:mi>T</mml:mi></mml:msub></mml:mrow></mml:math> &#61; 0.15 and 0.14eV, respectively. Both metastable atomic calcium states Ca(3P, 1D) were produced under low voltage dc-discharge conditions. By changing the discharge conditions, different metastable concentrations were produced to measure the state-to-state cross-section for both 3P and 1D reactions. The following values for the total chemiluminescence cross-sections were obtained:<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>&#x03C3;</mml:mi><mml:mrow><mml:mmultiscripts><mml:mtext>D</mml:mtext><mml:mprescripts /><mml:none /><mml:mn>1</mml:mn></mml:mmultiscripts></mml:mrow></mml:msub></mml:math> &#61; 1.77 &#197; and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>&#x03C3;</mml:mi><mml:mrow><mml:mmultiscripts><mml:mtext>P</mml:mtext><mml:mprescripts /><mml:none /><mml:mn>3</mml:mn></mml:mmultiscripts></mml:mrow></mml:msub></mml:math> &#61; 0.25 &#197; for the Ca(3P, 1D) + Cl4C &#8594; CaCl(A, B) + Cl3C reaction.<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>&#x03C3;</mml:mi><mml:mrow><mml:mmultiscripts><mml:mtext>D</mml:mtext><mml:mprescripts /><mml:none /><mml:mn>1</mml:mn></mml:mmultiscripts></mml:mrow></mml:msub></mml:math> &#61; 0.59 &#197;2 and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>&#x03C3;</mml:mi><mml:mrow><mml:mmultiscripts><mml:mtext>P</mml:mtext><mml:mprescripts /><mml:none /><mml:mn>3</mml:mn></mml:mmultiscripts></mml:mrow></mml:msub></mml:math> &#61; 0.56 &#197;2 for the Ca(3P, 1D) + SF6 &#8594; CaF(A) + SF5 reaction.<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>&#x03C3;</mml:mi><mml:mrow><mml:mmultiscripts><mml:mtext>D</mml:mtext><mml:mprescripts /><mml:none /><mml:mn>1</mml:mn></mml:mmultiscripts></mml:mrow></mml:msub></mml:math> &#61; 0.04 &#197;2 and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>&#x03C3;</mml:mi><mml:mrow><mml:mmultiscripts><mml:mtext>P</mml:mtext><mml:mprescripts /><mml:none /><mml:mn>3</mml:mn></mml:mmultiscripts></mml:mrow></mml:msub></mml:math> &#61; 0.12 &#197; for the Ca(3P, 1D) + SF6 &#8594; CaF(B) + SF5 reaction.In addition, beam-beam experiments were carried out at the same average low collision energy that of the beam-gas, and therefore, normalization between both experiments was possible. This procedure allowed us to obtain the excitation function of the Ca(1D) + SF6 reaction in absolute values over the 0.15&#8211;0.60eV collision energy range.On the other hand, by simulation, the ratio of CaCl(B-X/A-X) emissions intensities was found to be of 0.15. The variation of this ratio with the relative concentration of 1D/3P in a Broida oven leads to the conclusion that this state favours the formation of the B state in the chemiluminescent Ca(3P, 1D) + CH3CHCl2 &#8594; CaCl(A, B) + CH3CHCl reaction.

E.  Verdasco

M.  Men&#233;ndez

M.  Garay

A. Gonz&#225;lez Ure&#241;a

O. Benoist D&#39;azy

F. J. Poblete

G.  Ta&#239;eb

Reaction Dynamics of Electronically Excited Calcium Atom

A. Gonz&#xE1;lez Ure&#xF1;a

Laser Chemistry in Spain

In this work a spectroscopic method to measure the degradation degree of paraffinic mineral oils is proposed. The behaviour of some molecules (indoles) in solution versus their surrounding environment (solvent polarity and viscosity) is the basis of the method. Experimental results obtained for VESTAN oil, confirming this theoretical scheme, are presented.

M. Hern&#225;ndez Vi&#241;as

J. L. Escudero

A. L&#243;pez Campillo

E. Mart&#237;nez Murciano

T.  Montoro

Spectroscopic Sensor as a Mineral Oil Indicator

The vibrational spectra of classically chaotic systems are usually very complicated and seemingly unassignable. In this paper, two methods for the analysis of spectra of highly vibrationally excited polyatomic molecules are described, and some results for the floppy molecules HCN and LiNC are presented. By application of these methods, relevant information on the underlying dynamics is obtained, thus establishing a bridge between the spectroscopy and the dynamics of these systems.

F.  Borondo

J. M. Gomez Llorente

R. M. Benito

Theoretical Methods for the Analysis of Spectra of Highly Vibrationally Excited Polyatomic Molecules

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Laser Chemistry

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Articles

Direct Measurements of Removal Rates of CHF by Simple Alkenes

The Role of 6p States of Xe in the Discharge Pumped XeCl Laser Emission

Chemical Lasers From the Photodissociation of Nitrosyl Halides

A New Technique for Ultrafast Velocity Distribution Measurements of Atomic Species by Post-Ionization Laser Induced Fluorescence (PILIF)

Theoretical Approaches to Study the Vibrational Predissociation of Van Der Waals Molecules

New Directions in Multiphoton Dissociation

Reaction Dynamics of Electronically Excited Calcium Atom

Laser Chemistry in Spain

Spectroscopic Sensor as a Mineral Oil Indicator

Theoretical Methods for the Analysis of Spectra of Highly Vibrationally Excited Polyatomic Molecules