Transition State Spectroscopy of the Photoinduced Ca + CH₃F Reaction. 1. A Cluster Isolated Chemical Reaction Study

Abstract

The "Cluster Isolated Chemical Reactions" technique is used to examine the dynamics of the photoinduced reaction producing electronically excited CaF when 1:1 Ca · CH 3 F complexes are deposited at the surface of large argon clusters. This technique ensures quantitatively that 1:1 complexes are actually at the origin of the observed signals. The reaction is monitored by observing the CaF chemiluminescence while scanning the photoexcitation laser. The resulting action spectrum contains information about the absorption bands of the complex, filtered by the dynamics of the reaction. The observations suggest a profound alteration of the calcium electronic structure and a control of the reaction by the CF stretch in CH 3 F.

Transition State Spectroscopy of the Photoinduced Ca + CH3F Reaction. 2. Experimental and Ab Initio Studies of the Free Ca···FCH3 Complex

“…The experimental part of the present work took advantage of this property and indirectly confirmed the existence of such a barrier since it was possible to form a non reactive Ca · · · CH 3 F complex from which the reaction is turned on by photoexcitation. This was observed also in paper I of this series [1]. Hence, a local van der Waals well is expected to exist in the entrance channel of the ground state reaction that defines the equilibrium geometry of the complex.…”

“…The present paper is the second of a series [1] concerning the reaction Ca + CH 3 F → CaF + CH 3 ∆H = −80 kJ/mol = −0.83 eV.…”

“…[1] to account for the action spectrum in the CICR experiment. With the present discussion it accounts for the blue part of band B in the action spectrum of the free complex…”

Photochemical processes in doped argon-neon core-shell clusters: The effect of cage size on the dissociation of molecular oxygen

“…The size of these embedded clusters depends on the dopant gas density in the pickup region as for the helium droplets and is given by Poisson functions. 44 Molecular dynamics simulations have shown that the doping site in Ar clusters depends on the binding energy and the size of the dopant. 36 Further simulations on single and multiple doping of Ar clusters investigated the structural rearrangements and their time evolution in more detail 45,46 and provided results that agreed with the experimental findings by Rutzen et al 42 Owing to recent progress in the multiple pickup preparation techniques, it is now possible to cover the surface of embedded molecules or clusters with a well-defined number of atoms of a third material.…”

Cluster cross sections from pickup measurements: Are the established methods consistent?

“…1 Since then it has been developed into a very powerful tool in the cluster science: especially numerous experiments with large helium clusters use this technique [2][3][4] to study the spectroscopy of molecules [5][6][7][8][9][10] and their reactions [11][12][13][14][15] in the cold superfluid environment of the helium nanodroplets. Here we focus on the pickup to argon clusters which was also exploited in many studies, e.g., for cluster isolated chemical reactions on large Ar clusters in the group of Mestdagh 16,17 and others. 18 The pickup to argon and various other clusters was also employed for studies of photochemistry of molecules in cluster environment, [19][20][21][22] and in general for investigation of various mixed molecular clusters.…”