Structure and dynamics of the electronically excited C 1 and D 0+ states of ArXe from high-resolution vacuum ultraviolet spectra

Vacuum ultraviolet spectra of the C 1 ← X 0(+) and D 0(+) ← X 0(+) band systems of ArXe have been recorded at high resolution. Analysis of the rotational structure of the spectra of several isotopomers, and in the case of Ar(129)Xe and Ar(131)Xe also of the hyperfine structure, has led to the derivation of a complete set of spectroscopic parameters for the C 1 and D 0(+) states. The rovibrational energy level structure of the C 1 state reveals strong homogeneous perturbations with neighboring Ω = 1 electronic states. The analysis of isotopic shifts led to a reassignment of the vibrational structure of the C 1 state. The observation of electronically excited Xe fragments following excitation to the C state rotational levels of f parity indicates that the C state is predissociated by the electronic state of 0(-) symmetry associated with the Ar((1)S(0)) + Xe(6s(')[1/2](0) (o)) dissociation limit. The observed predissociation dynamics differ both qualitatively and quantitatively from the behavior reported in previous investigations. An adiabatic two-state coupling model has been derived which accounts for the irregularities observed in the rovibronic and hyperfine level structure of the C 1 state. The model predicts the existence of a second state of Ω = 1 symmetry, supporting several tunneling/predissociation resonances located ~200 cm(-1) above the C 1 state.     

Formation of ultracold metastable RbCs molecules by short-range photoassociation

Ultracold metastable RbCs molecules are observed in a double species magneto-optical trap through photoassociation near the Rb(5S(1/2)) + Cs(6P(3/2)) dissociation limit followed by radiative stabilization. The molecules are formed in their lowest triplet electronic state and are detected by resonance enhanced two-photon ionization through the previously unobserved (3)(3)Π ← a?(3)Σ(+) band. The large rotational structure of the observed photoassociation lines is assigned to the lowest vibrational levels of the 0(+) or 0(-) excited states correlated to the Rb(5P(1/2)) + Cs(6S(1/2)) dissociation limit. This demonstrates the possibility of inducing direct photoassociation in heteronuclear alkali-metal molecules at a short internuclear distance, as pointed out earlier [J. Deiglmayr et al., Phys. Rev. Lett., 2008, 101, 13304].     

Photoelectron imaging spectroscopy and theoretical investigation of ZrSi

The photoelectron spectrum of ZrSi(-) has been measured at two different photon energies: 2.33 eV and 3.49 eV, providing electron binding energy and photoelectron angular distribution information. The obtained vertical detachment energy of ZrSi(-) is 1.584(14) eV. The neutral ground and excited state terms are assigned based on experimental and theoretical results. The ground state of ZrSi is tentatively assigned as a (3)Σ(+) state with a configuration of 1σ(2) 1π(4) 1δ(0) 2σ(1) 3σ(1). A low lying (3)Π(i) neutral excited state is identified to be 0.238 eV (1919 cm(-1)) above the ground state. The anion ground state is designated as a (2)Σ(+) state with a 1σ(2) 1π(4) 1δ(0) 2σ(2) 3σ(1) valence electron configuration. A Franck-Condon (FC) simulation of the photoelectron spectrum has been carried out. For the (3)Σ(+) ← (2)Σ(+) band, theoretically calculated bond lengths and frequencies are used in the FC calculation which give good agreement with experiment, while for the (3)Π(i) ← (2)Σ(+) band, the ZrSi bond length is estimated from the FC spectrum. Comparisons are made with previously published theoretical studies and inconsistencies are pointed out. To the best of our knowledge, this study provides the first spectroscopic information on the transition metal-silicon diatomic, ZrSi.     

Infrared vacuum-ultraviolet laser pulsed field ionization-photoelectron study of CH3Br+ (X(2)E(3/2))

By preparing methyl bromide (CH3Br) in selected rotational levels of the CH3Br(X(1)A1; v1 = 1) state with infrared (IR) laser excitation prior to vacuum-ultraviolet (VUV) laser pulsed field ionization-photoelectron (PFI-PE) measurements, we have observed rotationally resolved photoionization transitions to the CH3Br(+)(X(2)E(3/2); v1(+) = 1) state, where v1 and v1(+) are the symmetric C-H stretching vibrational mode for the neutral and cation, respectively. The VUV-PFI-PE origin band for CH3Br(+)(X(2)E(3/2)) has also been measured. The simulation of these IR-VUV-PFI-PE and VUV-PFI-PE spectra have allowed the determination of the v1(+) vibrational frequency (2901.8 +/- 0.5 cm(-1)) and the ionization energies of the origin band (85 028.3 +/- 0.5 cm(-1)) and the v1(+) = 1 <-- v1 = 1 band (84 957.9 +/- 0.5 cm(-1)).     

Infrared overtone spectroscopy and unimolecular decay dynamics of peroxynitrous acid

Peroxynitrous acid (HOONO) is generated in a pulsed supersonic expansion through recombination of photolytically generated OH and NO(2) radicals. A rotationally resolved infrared action spectrum of HOONO is obtained in the OH overtone region at 6971.351(4) cm(-1) (origin), providing definitive spectroscopic identification of the trans-perp (tp) conformer of HOONO. Analysis of the rotational band structure yields rotational constants for the near prolate asymmetric top, the ratio of the a-type to c-type components of the transition dipole moment for the hybrid band, and a homogeneous linewidth arising from intramolecular vibrational energy redistribution and/or dissociation. The quantum state distribution of the OH (nu=0,J(OH)) products from dissociation is well characterized by a microcanonical statistical distribution constrained only by the energy available to products, 1304+/-38 cm(-1). This yields a 5667+/-38 cm(-1) [16.2(1) kcal mol(-1)] binding energy for tp-HOONO. An equivalent available energy and corresponding binding energy are obtained from the highest observed OH product state. Complementary high level ab initio calculations are carried out in conjunction with second-order vibrational perturbation theory to predict the spectroscopic observables associated with the OH overtone transition of tp-HOONO including its vibrational frequency, rotational constants, and transition dipole moment. The same approach is used to compute frequencies and intensities of multiple quantum transitions that aid in the assignment of weaker features observed in the OH overtone region, in particular, a combination band of tp-HOONO involving the HOON torsional mode.     

Communication: determination of the bond dissociation energy (D0) of the water dimer, (H2O)2, by velocity map imaging

The bond dissociation energy (D(0)) of the water dimer is determined by using state-to-state vibrational predissociation measurements following excitation of the bound OH stretch fundamental of the donor unit of the dimer. Velocity map imaging and resonance-enhanced multiphoton ionization (REMPI) are used to determine pair-correlated product velocity and translational energy distributions. H(2)O fragments are detected in the ground vibrational (000) and the first excited bending (010) states by 2 + 1 REMPI via the C? (1)B(1) (000) ← X? (1)A(1) (000 and 010) transitions. The fragments' velocity and center-of-mass translational energy distributions are determined from images of selected rovibrational levels of H(2)O. An accurate value for D(0) is obtained by fitting both the structure in the images and the maximum velocity of the fragments. This value, D(0) = 1105 ± 10 cm(-1) (13.2 ± 0.12 kJ/mol), is in excellent agreement with the recent theoretical value of D(0) = 1103 ± 4 cm(-1) (13.2 ± 0.05 kJ∕mol) suggested as a benchmark by Shank et al. [J. Chem. Phys. 130, 144314 (2009)].     

Mass analyzed threshold ionization spectra of phenol...Ar2: ionization energy and cation intermolecular vibrational frequencies

The phenol(+)...Ar(2) complex has been characterized in a supersonic jet by mass analyzed threshold ionization (MATI) spectroscopy via different intermediate intermolecular vibrational states of the first electronically excited state (S(1)). From the spectra recorded via the S(1)0(0) origin and the S(1)β(x) intermolecular vibrational state, the ionization energy (IE) has been determined as 68,288 ± 5 cm(-1), displaying a red shift of 340 cm(-1) from the IE of the phenol(+) monomer. Well-resolved, nearly harmonic vibrational progressions with a fundamental frequency of 10 cm(-1) have been observed in the ion ground state (D(0)) and assigned to the symmetric van der Waals (vdW) bending mode, β(x), along the x axis containing the C-O bond. MATI spectra recorded via the S(1) state involving other higher-lying intermolecular vibrational states (σ(s)(1), β(x)(3), σ(s)(1)β(x)(1), σ(s)(1)β(x)(2)) are characterized by unresolved broad structures.     

The Al+ -H(2) cation complex: rotationally resolved infrared spectrum, potential energy surface, and rovibrational calculations

The infrared spectrum of the Al(+)-H(2) complex is recorded in the H-H stretch region (4075-4110 cm(-1)) by monitoring Al(+) photofragments. The H-H stretch band is centered at 4095.2 cm(-1), a shift of -66.0 cm(-1) from the Q(1)(0) transition of the free H(2) molecule. Altogether, 47 rovibrational transitions belonging to the parallel K(a)=0-0 and 1-1 subbands were identified and fitted using a Watson A-reduced Hamiltonian, yielding effective spectroscopic constants. The results suggest that Al(+)-H(2) has a T-shaped equilibrium configuration with the Al(+) ion attached to a slightly perturbed H(2) molecule, but that large-amplitude intermolecular vibrational motions significantly influence the rotational constants derived from an asymmetric rotor analysis. The vibrationally averaged intermolecular separation in the ground vibrational state is estimated as 3.03 A, decreasing by 0.03 A when the H(2) subunit is vibrationally excited. A three-dimensional potential energy surface for Al(+)-H(2) is calculated ab initio using the coupled cluster CCSD(T) method and employed for variational calculations of the rovibrational energy levels and wave functions. Effective dissociation energies for Al(+)-H(2)(para) and Al(+)-H(2)(ortho) are predicted, respectively, to be 469.4 and 506.4 cm(-1), in good agreement with previous measurements. The calculations reproduce the experimental H-H stretch frequency to within 3.75 cm(-1), and the calculated B and C rotational constants to within approximately 2%. Agreement between experiment and theory supports both the accuracy of the ab initio potential energy surface and the interpretation of the measured spectrum.     

Electronic states and spin-orbit splitting of lanthanum dimer

Lanthanum dimer (La(2)) was studied by mass-analyzed threshold ionization (MATI) spectroscopy and a series of multi-configuration ab initio calculations. The MATI spectrum exhibits three band systems originating from ionization of the neutral ground electronic state, and each system shows vibrational frequencies of the neutral molecule and singly charged cation. The three ionization processes are La(2)(+) (a(2)∑(g)(+)) ← La(2) (X(1)∑(g)(+)), La(2)(+) (b(2)Π(3/2, u)) ← La(2) (X(1)∑(g)(+)), and La(2)(+) (b(2)Π(1/2, u)) ← La(2) (X(1)∑(g)(+)), with the ionization energies of 39,046, 40,314, and 40,864 cm(-1), respectively. The vibrational frequency of the X(1)Σ(g)(+) state is 207 cm(-1), and those of the a(2)Σ(g)(+), b(2)Π(3/2, u) and b(2)Π(1/2, u) are 235.7, 242.2, and 240 cm(-1). While X(1)Σ(g)(+) is the ground state of the neutral molecule, a(2)Σ(g (+) and b(2)Π(u) are calculated to be the excited states of the cation. The spin-orbit splitting in the b(2)Π(u) ion is 550 cm(-1). An X(4)Σ(g)(-) state of La(2)(+) was predicted by theory, but not observed by the experiment. The determination of a singlet ground state of La(2) shows that lanthanum behaves differently from scandium and yttrium.     

Anharmonic vibrational frequencies and vibrationally averaged structures and nuclear magnetic resonance parameters of FHF-

The anharmonic vibrational frequencies of FHF(-) were computed by the vibrational self-consistent-field, configuration-interaction, and second-order perturbation methods with a multiresolution composite potential energy surface generated by the electronic coupled-cluster method with various basis sets. Anharmonic vibrational averaging was performed for the bond length and nuclear magnetic resonance indirect spin-spin coupling constants, where the latter computed by the equation-of-motion coupled-cluster method. The calculations placed the vibrational frequencies at 580 (nu(1)), 1292 (nu(2)), 1313 (nu(3)), 1837 (nu(1) + nu(3)), and 1864 cm(-1) (nu(1) + nu(2)), the zero-point H-F bond length (r(0)) at 1.1539 A, the zero-point one-bond spin-spin coupling constant [(1)J(0)(HF)] at 124 Hz, and the bond dissociation energy (D(0)) at 43.3 kcal/mol. They agreed excellently with the corresponding experimental values: nu(1) = 583 cm(-1), nu(2) = 1286 cm(-1), nu(3) = 1331 cm(-1), nu(1) + nu(3) = 1849 cm(-1), nu(1) + nu(2) = 1858 cm(-1), r(0) = 1.1522 A, (1)J(0)(HF) = 124+/-3 Hz, and D(0) = 44.4+/-1.6 kcal/mol. The vibrationally averaged bond lengths matched closely the experimental values of five excited vibrational states, furnishing a highly dependable basis for correct band assignments. An adiabatic separation of high- (nu(3)) and low-frequency (nu(1)) stretching modes was examined and found to explain semiquantitatively the appearance of a nu(1) progression on nu(3). Our calculations predicted a value of 186 Hz for experimentally inaccessible (2)J(0)(FF).     

Electronic spectroscopy and electronic structure of diatomic TiFe

Diatomic TiFe, a 12 valence electron molecule that is isoelectronic with Cr(2), has been spectroscopically investigated for the first time. In addition, the first computational study that includes the ground and excited electronic states is reported. Like Cr(2), TiFe has a (1)Σ(+) ground state that is dominated by the 1σ(2) 2σ(2) 1π(4) 1δ(4) configuration. Rotationally resolved spectroscopy has established a ground state bond length of 1.7024(3) A?, quite similar to that found for Cr(2) (r(0) = 1.6858 A?). Evidently, TiFe exhibits a high degree of multiple bonding. The vibronic spectrum is highly congested and intense to the blue of 20?000 cm(-1), while two extremely weak band systems, the [15.9](3)Π(1) ← X (1)Σ(+) and [16.2](3)Π(0+) ← X (1)Σ(+) systems, are found in the 16?000-18?500 cm(-1) region. The bond lengths, obtained by inversion of the B(e) (') values, and vibrational frequencies of the two upper states are nearly identical: 1.886?A? and 344 cm(-1) for [15.9](3)Π(1) and 1.884 A? and 349 cm(-1) for [16.2](3)Π(0+). The measured spin-orbit splitting of the (3)Π state is consistent with its assignment to the 1σ(2) 2σ(2) 1π(4) 1δ(3) 2π(1) configuration, as is also found in the ab initio calculations.     

Vibrational spectroscopy of the pyridazine cation in the ground state

Vibrational structure of the pyridazine cation in the ground state has been revealed by a vacuum-ultraviolet mass-analyzed threshold ionization (VUV-MATI) spectroscopy. The adiabatic ionization energy is precisely measured to be 70241 +/- 6 cm(-1) (8.7088 +/- 0.0007 eV). The origin is very weakly observed, while a long progression of the nu9(+) (a1) band of which the fundamental vibrational frequency is 647 cm(-1) is predominantly observed. The nu9(+) (a1) mode progression combined with one quantum of the nu3(+) (a1) band at 1698 cm(-1) is found to be even stronger. Many other weakly observed vibrational features of the pyridazine cation are identified in the vibrational energy of 0-3500 cm(-1). The structural change of pyridazine upon ionization, reflected in the vibrational spectrum obtained by the one-photon direct ionization process, is theoretically predicted by ab initio calculations. Ring distortion including contraction of the N=N bond should be responsible for strong excitations of nu3(+) and nu9(+) modes. Franck-Condon analysis is given for the comparison of the experiment and theory.     

Second OH overtone excitation and statistical dissociation dynamics of peroxynitrous acid

The second OH overtone transition of the trans-perp conformer of peroxynitrous acid (tp-HOONO) is identified using infrared action spectroscopy. HOONO is produced by the recombination of photolytically generated OH and NO(2) radicals, and then cooled in a pulsed supersonic expansion. The second overtone transition is assigned to tp-HOONO based on its vibrational frequency (10 195.3 cm(-1)) and rotational band contour, which are in accord with theoretical predictions and previous observations of the first overtone transition. The transition dipole moment associated with the overtone transition is rotated considerably from the OH bond axis, as evident from its hybrid band composition, indicating substantial charge redistribution upon OH stretch excitation. The overtone band exhibits homogeneous line broadening that is attributed to intramolecular vibrational redistribution, arising from the coupling of the initially excited OH stretch to other modes that ultimately lead to dissociation. The quantum state distributions of the OH X (2)Pi (nu=0) products following first and second OH overtone excitation of tp-HOONO are found to be statistical by comparison with three commonly used statistical models. The product state distributions are principally determined by the tp-HOONO binding energy of 16.2(1) kcal mol(-1). Only a small fraction of the OH products are produced in nu=1 following the second overtone excitation, consistent with statistical predictions.     

Overtone-induced dissociation and isomerization dynamics of the hydroxymethyl radical (CH2OH and CD2OH). II. Velocity map imaging studies

The dissociation of the hydroxymethyl radical, CH(2)OH, and its isotopolog, CD(2)OH, following excitation in the 4ν(1) region (OH stretch overtone, near 13,600 cm(-1)) was studied using sliced velocity map imaging. A new vibrational band near 13,660 cm(-1) arising from interaction with the antisymmetric CH stretch was discovered for CH(2)OH. In CD(2)OH dissociation, D atom products (correlated with CHDO) were detected, providing the first experimental evidence of isomerization in the CH(2)OH ? CH(3)O (CD(2)OH ? CHD(2)O) system. Analysis of the H (D) fragment kinetic energy distributions shows that the rovibrational state distributions in the formaldehyde cofragments are different for the OH bond fission and isomerization pathways. Isomerization is responsible for 10%-30% of dissociation events in all studied cases, and its contribution depends on the excited vibrational level of the radical. Accurate dissociation energies were determined: D(0)(CH(2)OH → CH(2)O + H) = 10,160 ± 70 cm(-1), D(0)(CD(2)OH → CD(2)O + H) = 10,135 ± 70 cm(-1), D(0)(CD(2)OH → CHDO + D) = 10,760 ± 60 cm(-1).     

Xe+ formation following photolysis of Au-Xe: a velocity map imaging study

The photodissociation dynamics of Au-Xe leading to Xe(+) formation via the Ξ(1∕2)-X(2)Σ(+) (v('), 0) band system (41?500-41?800 cm(-1)) have been investigated by velocity map imaging. Five product channels have been indentified, which can be assigned to photoinduced charge transfer followed by photodissociation in either the neutral or the [Au-Xe](+) species. For the neutral species, charge transfer occurs via a superexcited Rydberg state prior to dissociative ionization, while single-photon excitation of the gold atom in Au(+)-Xe accesses an (Au(+))?-Xe excited state that couples to a dissociative continuum in Au-Xe(+). Mechanisms by which charge transfer occurs are proposed, and branching ratios for Xe(+) formation via the superexcited Rydberg state are reported. The bond dissociation energy for the first excited state of Au(+)-Xe is determined to be ～9720 ± 110 cm(-1).     

Imaging H2O photofragments in the predissociation of the HCl-H2O hydrogen-bonded dimer

The state-to-state vibrational predissociation (VP) dynamics of the hydrogen-bonded HCl-H(2)O dimer was studied following excitation of the dimer's HCl stretch by detecting the H(2)O fragment. Velocity map imaging (VMI) and resonance-enhanced multiphoton ionization (REMPI) were used to determine pair-correlated product energy distributions. Following vibrational excitation of the HCl stretch of the dimer, H(2)O fragments were detected by 2 + 1 REMPI via the C (1)B(1) (000) ← X (1)A(1) (000) transition. REMPI spectra clearly show H(2)O from dissociation produced in the ground vibrational state. The fragments' center-of-mass (c.m.) translational energy distributions were determined from images of selected rotational states of H(2)O and were converted to rotational state distributions of the HCl cofragment. The distributions were consistent with the previously measured dissociation energy of D(0) = 1334 ± 10 cm(-1) and show a clear preference for rotational levels in the HCl fragment that minimize translational energy release. The usefulness of 2 + 1 REMPI detection of water fragments is discussed.     

Parallel and coupled perpendicular transitions of RbCs 640 nm system: mass-resolved resonance enhanced two-photon ionization in a cold molecular beam

We have investigated the RbCs 640 nm system by mass-resolved resonance enhanced two-photon ionization in a cold molecular beam. Very complex vibronic structures were observed between 15420 and 15990 cm (-1). The parallel transitions of 2 (3)Pi 0 v' = 4-20 <-- X (1)Sigma (+) v' = 0 were identified by rotationally resolved spectra. Molecular constants and a Rydberg-Klein-Rees potential energy curve of the 2 (3)Pi 0 state were determined. The regular vibrational spacing of the parallel transition indicated that the 2 (3)Pi 0 state is not significantly perturbed by nearby excited electronic states. The complexity of the observed vibronic structures has been attributed to the coupled perpendicular transitions of 2 (1)Pi, 2 (3)Pi 1, and 3 (3)Sigma 1 (+) <-- X (1)Sigma (+) v' = 0. For the perpendicular bands observed in the lower-energy spectral region between 15420 and 15630 cm (-1) where the onsets of the 2 (3)Pi 1 and 3 (3)Sigma 1 (+) <-- X (1)Sigma (+) transitions are located, the upper electronic states and the vibrational quantum numbers were assigned. Perturbations of 2 (3)Pi 1-3 (3)Sigma 1 (+) and 2 (1)Pi-3 (3)Sigma 1 (+) have been identified by the observed level shifts.     

The electronic spectrum of Si3 I: triplet D(3h) system

We report the measurement of a jet-cooled electronic spectrum of the silicon trimer. Si(3) was produced in a pulsed discharge of silane in argon, and the excitation spectrum examined in the 18 000-20 800 cm(-1) region. A combination of resonant two-color two-photon ionization (R2C2PI) time-of-flight mass spectroscopy, laser-induced fluorescence/dispersed fluorescence, and equation-of-motion coupled-cluster calculations have been used to establish that the observed spectrum is dominated by the 1(3)A(1)" - a? (3)A(2)' transition of the D(3h) isomer. The spectrum has an origin transition at 18,600 ± 4 cm(-1) and a short progression in the symmetric stretch with a frequency of ～445 cm(-1), in good agreement with a predicted vertical transition energy of 2.34 eV for excitation to the 1(3)A(1)" state, which has a calculated symmetric stretching frequency of 480 cm(-1). In addition, a ～505 cm(-1) ground state vibrational frequency determined from sequence bands and dispersed fluorescence is in agreement with an earlier zero-electron kinetic energy study of the lowest D(3h) state and with theory. A weaker, overlapping band system with a ～360 cm(-1) progression, observed in the same mass channel (m/z = 84) by R2C2PI but under different discharge conditions, is thought to be due to transitions from the (more complicated) singlet C(2v) ground state ((1)A(1)) state of Si(3). Evidence of emission to this latter state in the triplet dispersed fluorescence spectra suggests extensive mixing in the excited triplet and singlet manifolds. Prospects for further spectroscopic characterization of the singlet system and direct measurement of the energy separation between the lowest singlet and triplet states are discussed.     

1 Pi<--X1 Sigma+ band systems of jet-cooled ScCo and YCo

Rotationally resolved resonant two-photon ionization (R2PI) spectra of ScCo and YCo are reported. The measured spectra reveal that these molecules possess ground electronic states of (1)Sigma(+) symmetry, as previously found in the isoelectronic Cr(2) and CrMo molecules. The ground state rotational constants for ScCo and YCo are B(0)(")=0.201 31(22) cm(-1) and B(0) (")=0.120 96(10) cm(-1), corresponding to ground state bond lengths of r(0) (")=1.812 1(10) A and r(0) (")=1.983 0(8) A, respectively. A single electronic band system, assigned as a (1)Pi<--X (1)Sigma(+) transition, has been identified in both molecules. In ScCo, the (1)Pi state is characterized by T(0)=15,428.8, omega(e)(')=246.7, and omega(e)(')x(e)(')=0.73 cm(-1). In YCo, the (1)Pi state has T(0)=13 951.3, omega(e)(')=231.3, and omega(e)(')x(e) (')=2.27 cm(-1). For YCo, hot bands originating from levels up to v(")=3 are observed, allowing the ground state vibrational constants omega(e)(")=369.8, omega(e)(")x(e)(")=1.47, and Delta G(12)(")=365.7 cm(-1) to be deduced. The bond energy of ScCo has been measured as 2.45 eV from the onset of predissociation in a congested vibronic spectrum. A comparison of the chemical bonding in these molecules to related molecules is presented.     

High-resolution slice imaging of quantum state-to-state photodissociation of methyl bromide

The photodissociation of rotationally state-selected methyl bromide is studied in the wavelength region between 213 and 235 nm using slice imaging. A hexapole state selector is used to focus a single (JK=11) rotational quantum state of the parent molecule, and a high speed slice imaging detector measures directly the three-dimensional recoil distribution of the methyl fragment. Experiments were performed on both normal (CH(3)Br) and deuterated (CD(3)Br) parent molecules. The velocity distribution of the methyl fragment shows a rich structure, especially for the CD(3) photofragment, assigned to the formation of vibrationally excited methyl fragments in the nu(1) and nu(4) vibrational modes. The CH(3) fragment formed with ground state Br((2)P(3/2)) is observed to be rotationally more excited, by some 230-340 cm(-1), compared to the methyl fragment formed with spin-orbit excited Br((2)P(1/2)). Branching ratios and angular distributions are obtained for various methyl product states and they are observed to vary with photodissociation energy. The nonadiabatic transition probability for the (3)Q(0+)-->(1)Q(1) transition is calculated from the images and differences between the isotopes are observed. Comparison with previous non-state-selected experiments indicates an enhanced nonadiabatic transition probability for state-selected K=1 methyl bromide parent molecules. From the state-to-state photodissociation experiments the dissociationenergy for both isotopes was determined, D(0)(CH(3)Br)=23 400+/-133 cm(-1) and D(0)(CD(3)Br)=23 827+/-94 cm(-1).