^{1,a)}, Hsu Chen Hsu

^{1,b)}, Yuan Chin Hsu

^{1,a)}and Chi-Kung Ni

^{1,a),c)}

### Abstract

Energy transfer between highly vibrationally excited naphthalene and Kr atom in a series of translational collisionenergies was studied separately using a crossed-beam apparatus along with time-sliced velocity map ion imaging techniques. Highly vibrationally excited naphthalene in the triplet state (vibrational energy:; electronic energy:) was formed via the rapid intersystem crossing of naphthalene initially excited to the state by photons. The collisional energy transferprobability density functions were measured directly from the scattering results of highly vibrationally excited naphthalene. At low collisionenergies a short-lived naphthalene-Kr complex was observed, resulting in small amounts of translational to vibrational-rotational energy transfer. The complex formation probability decreases as the collisionenergy increases. energy transfer was found to be quite efficient at all collisionenergies. In some instances, nearly all of the translational energy is transferred to vibrational-rotational energy. On the other hand, only a small fraction of vibrational energy is converted to translational energy. The translational energy gained from vibrational energy extend to large energy transfer (up to ) as the collisionenergy increases to . Substantial amounts of large energy transfer were observed in the forward and backward directions at large collisionenergies.

We thank Professor Y. L. Lee and Professor I. Oref for many helpful discussions. The work was supported by the National Science Council (NSC) of Taiwan, under Contract No. NSC 95-2113-M-001-051.

I. INTRODUCTION

II. EXPERIMENT

III. RESULTS

IV. DISCUSSION

A. Large energy transfer and supercollisions

B. The role of naphthalene-Kr van der Waals complex

C. Comparison to azulene-Kr collisions

### Key Topics

- Energy transfer
- 110.0
- Atomic and molecular beams
- 35.0
- Vibrational energy transfer
- 24.0
- Forward scattering
- 18.0
- Probability density functions
- 12.0

## Figures

Schematic diagram of the crossed-molecular beam apparatus. Only the 25° crossing geometry is shown.

Schematic diagram of the crossed-molecular beam apparatus. Only the 25° crossing geometry is shown.

Energy diagram of naphthalene and corresponding photon energy.

Energy diagram of naphthalene and corresponding photon energy.

(Color) Images and Newton diagrams for collision energies of (a) 226, (b) 421, (c) 612, and (d) .

(Color) Images and Newton diagrams for collision energies of (a) 226, (b) 421, (c) 612, and (d) .

Angular dependence of and cross sections at various collision energies.

Angular dependence of and cross sections at various collision energies.

Angular resolved energy transfer probability density functions. The thick black line represents near forward scatterings , the thin black line represents sideway scattering , and the thick gray line represents backward scatterings . In the left column, the sideway and backward scatterings have been multiplied by some factors, respectively, such that they and forward scattering have the same value at . In the right column, they are plotted in the same scale.

Angular resolved energy transfer probability density functions. The thick black line represents near forward scatterings , the thin black line represents sideway scattering , and the thick gray line represents backward scatterings . In the left column, the sideway and backward scatterings have been multiplied by some factors, respectively, such that they and forward scattering have the same value at . In the right column, they are plotted in the same scale.

Angular resolved energy transfer probability density functions. The thick black line represents near forward scatterings ( for the first column and for the second column), the thin black line represents sideway scattering , and the thick gray line represents backward scatterings . In the left column, the sideway and backward scatterings have been multiplied by some factors, respectively, such that they and forward scattering have the same value at . In the right column, they are plotted in the same scale.

Angular resolved energy transfer probability density functions. The thick black line represents near forward scatterings ( for the first column and for the second column), the thin black line represents sideway scattering , and the thick gray line represents backward scatterings . In the left column, the sideway and backward scatterings have been multiplied by some factors, respectively, such that they and forward scattering have the same value at . In the right column, they are plotted in the same scale.

Energy transfer probability density functions at various collision energies. (a) dotted line: ; (b) thick gray line: ; (c) thin black line: ; (d) thick black line: . Negative values represent energy down energy transfer and positive values represent energy up energy transfer.

Energy transfer probability density functions at various collision energies. (a) dotted line: ; (b) thick gray line: ; (c) thin black line: ; (d) thick black line: . Negative values represent energy down energy transfer and positive values represent energy up energy transfer.

## Tables

Velocity uncertainties and speed ratios of naphthalene molecular beam, average energy transfer of complex, and average energy transfer at various collision energies. and are the full widths at half maximum of the naphthalene velocity distribution in and directions, respectively. , naphthalene velocity in the laboratory frame; , naphthalene velocity in the center of mass frame; . complex is the average energy transfer from the complex, is the average energy transfer. Negative values represent energy down energy transfer and positive values represent energy up energy transfer.

Velocity uncertainties and speed ratios of naphthalene molecular beam, average energy transfer of complex, and average energy transfer at various collision energies. and are the full widths at half maximum of the naphthalene velocity distribution in and directions, respectively. , naphthalene velocity in the laboratory frame; , naphthalene velocity in the center of mass frame; . complex is the average energy transfer from the complex, is the average energy transfer. Negative values represent energy down energy transfer and positive values represent energy up energy transfer.

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