Jane M. Behm

The 846 nm A’ 3Σ−u←X 3Σ−g band system of jet‐cooled V2

The 846 nm band system of jet‐cooled 51V2 has been recorded using resonant two‐photon ionization spectroscopy, and is assigned as the A’ 3Σ−u←X 3Σ−g band system. Both the Ω’=1u←Ω‘=1g and Ω’=0+u←Ω‘=0+g subbands of the 0–0 band have been rotationally resolved and analyzed. Although the transition could, in principle, correspond to a π*g←πu or σ*u←σg excitation, it is assigned as a δ*u←δg excitation. Either of the other two possibilities makes it difficult to rationalize the small reduction in bond length which accompanies the excitation [re(X 3Σ−g)=1.77 A, r0(A’ 3Σ−u)=1.756 A]. In addition, the second order spin–orbit splitting of the ground X 3Σ−g state is reanalyzed to predict the existence of a 1Σ+g state, arising from the same sσ2gdσ2gdπ4udδ2g electronic configuration as the X 3Σ−g ground state, at an energy about 1821 cm−1 above the ground state.This allows a state previously observed in an electronic resonance Raman effect 1860 cm−1 above the ground state to be positively identified as the sσ2gdσ2gdπ4...

Spectroscopic studies of jet‐cooled AlNi

Resonant two‐photon ionization spectroscopy has been applied to jet‐cooled diatomic CuAg. Four band systems have been observed, three of which have been rotationally resolved and analyzed. The ground state is X 1Σ+ in symmetry, deriving from the 3d10Cu4d10Agσ2 molecular configuration. Its bond length has been determined as r0=2.3735±0.0006 A (1σ error limits). Based on an analysis of the possible separated atom limits, three of the excited states observed (A 0+, A’ 1, and B’ 0+ ) are assigned as primarily 3d9Cu4d10Agσ2σ* in character. The observation of unusually large electronic isotope shifts in the A–X, A’–X, and B’–X band systems, similar in magnitude to those previously observed in the A–X and B–X systems of Cu2 and the s←d excitations in atomic copper, provides further confirmation that these excited states derive from the 3d9Cu4d10Agσ2σ* molecular configuration. Finally, the highest energy state observed in this work is argued to be primarily ion pair in character, and is expected to have significa...

Spectroscopic analysis of the open 3d subshell transition metal aluminides: AlV, AlCr, and AlCo

Three open 3d subshell transition metal aluminides, AlV, AlCr, and AlCo, have been investigated by resonant two‐photon ionization spectroscopy to elucidate the chemical bonding in these diatomic molecules. The open nature of the 3d subshell results in a vast number of excited electronic states in these species, allowing bond strengths to be measured by the observation of abrupt predissociation thresholds in a congested optical spectrum, giving D00(AlV)=1.489±0.010 eV, D00(AlCr)=2.272±0.009 eV, and D00(AlCo)=1.844±0.002 eV. At lower excitation energies the presence of discrete transitions has permitted determinations of the ground state symmetries and bond lengths of AlV and AlCo through rotationally resolved studies, giving r0‘ (AlV, Ω‘=0)=2.620±0.004 A and r0‘ (AlCo, Ω‘=3)=2.3833±0.0005 A. Ionization energies were also measured for all three species, yielding IE(AlV)=6.01±0.10 eV, IE(AlCr)=5.96±0.04 eV, and IE(AlCo)=6.99±0.17 eV. A discussion of these results is presented in the context of previous work ...

Spectroscopic analysis of jet‐cooled AlCu

Diatomic AlCu has been interrogated using resonant two‐photon ionization spectroscopy in a supersonic expansion of helium. The ground state is shown to be X 1Σ+, deriving from the 3sAl23dCu10σ2 configuration, in agreement with theoretical predictions. The closed‐shell nature of this molecule results in a low density of electronic states, allowing the chemical bonding and electronic structure to be investigated in detail. Five excited electronic states have been observed and characterized, leading to a potential energy diagram based solely on experimental results. Constants experimentally determined for AlCu include a ground state bond length (r0) of 2.3389±0.0004 A, a dissociation energy, D0○, of 2.315±0.012 eV, and an ionization potential of 7.065±0.014 eV.

Resonant two‐photon ionization spectroscopy of coinage metal trimers: Cu2Ag, Cu2Au, and CuAgAu

The jet‐cooled coinage metal triatomic molecules Cu2Ag, Cu2Au, and CuAgAu have been investigated using resonant two‐photon ionization spectroscopy. One band system, labeled as the A–X system, has been observed for each species, with origin bands at 13 188, 17 217, and 17 470 cm−1, respectively. Vibrational progressions have been assigned and vibrational constants have been extracted using a linear least‐squares fitting procedure. For Cu2Ag, 47 vibrational bands have been assigned within the A–X system. The upper states of these bands derive from combinations of two symmetric (a1) and one antisymmetric (b2) mode in the C2v point group. For the A–X system of Cu2Au, only seven vibrational bands have been observed, all occurring within a 500 cm−1 range. Lifetime measurements for the observed vibrational levels support the possibility that predissociation may be occurring in the A excited state of Cu2Au and this may be limiting the number of vibrational levels observed within this state. Finally, in the...

The A 1Σ+ ← X 1Σ+ band system of CrMo

Abstract The 4870 A band system of jet-cooled CrMo has been rotationally resolved and assigned as A 1 Σ + ← X 1 Σ + . The band system is clearly analogous to the 4597 A band system of Cr 2 and the 5180 A band system of Mo 2 . As in the Cr 2 and Mo 2 systems, the upper state possesses a very short fluorescence lifetime, which has been measured as 14.7 ± 0.3 ns. The bond lengths of the ground and excited states are r e (X 1 Σ + ) = 1.8182±0.0015 A and r e (A 1 Σ + ) = 1.8264±0.0014 A, respectively. These results clearly establish that CrMo, like Cr 2 and Mo 2 , possesses multiple d electron bonds in its ground (X 1 Σ + ) and excited (A 1 Σ + ) electronic states.

Interaction of an aluminum atom with an alkaline earth atom: Spectroscopic and ab initio investigations of AlCa

A spectroscopic analysis of diatomic AlCa generated by laser vaporization of a 2:1 Al:Ca metal alloy followed by supersonic expansion has been completed using resonant two‐photon ionization spectroscopy. Four excited electronic states have been identified and investigated in the energy region from 13 500 to 17 900 cm−1. These are the [13.5] 2Πr, the [15.8] 2Σ, the [17.0] 2Δ3/2(?), and the [17.6] 2Δ3/2 states. From rotational analysis excited state bond lengths have been measured for three of the four excited states, and the ground state has been unambiguously determined as a 2Πr state with a weighted least squares value of the ground state bond length of r0‘ = 3.1479± 0.0010 A. The ionization energy of the molecule has also been directly determined as 5.072±0.028 eV. Ab initio calculations for the potential energy curves of seven low‐lying states of AlCa [X 2Πr, 2Σ+, 4Σ−, 4Πr, 2Πr(2), 2Δ, and 2Σ−] and for the X 1Σ+ ground electronic state of AlCa+ have been carried out. In agreement with experiment, 2Πr i...

Interaction of an aluminum atom with a closed subshell metal atom: Spectroscopic analysis of AlZn

Resonant two‐photon ionization spectroscopy has been employed to investigate diatomic AlZn produced by laser vaporization of a 1:2 Al:Zn alloy target disk in a supersonic expansion of helium. Several discrete transitions are reported in the energy range from 18 400 to 19 100 cm−1. Most of these are assigned as members of the B 2Π←X 2Π system, although an isolated band has been observed and assigned as the 2‐0 band of the A Ω’=0.5←X 2Π1/2 system. A pair of strongly mixed levels are identified as resulting from a homogeneous spin–orbit perturbation between the A Ω=0.5, v’=3 and the B 2Π1/2, v’=1 levels, and the perturbation matrix element has been deduced to be 8.11 cm−1 for 27Al64Zn, 8.23 cm−1 for 27Al66Zn. The ground state has been unambiguously identified as a 2Πr state with a bond length of 2.6957±0.0004 A. Comparisons to the results of the preceding article on the spectroscopy of AlCa are also provided, along with a discussion of the chemical bonding in AlZn in relation to AlCa, AlAr, and AlKr.

Spectroscopy of jet-cooled AlMn and trends in the electronic structure of the 3d transition metal aluminides

Jet‐cooled diatomic AlMn has been spectroscopically investigated and is shown to possess a 5Πi ground state deriving from the Al (3s23p1,2P0)+Mn (3d54s2,6S) separated atom limit. This implies that the aluminum atom favors a 3pπ approach to the manganese atom, a result that is in agreement with previous studies on the related AlCa and AlZn molecules. The ground state bond length has been measured as 2.6384±0.0010 A, a value which includes corrections due to spin–uncoupling effects in the X 5Πi state. It is suggested that the 5Πi state emerges as the ground state due to a particularly favorable configuration interaction with a low‐lying 5Πi state that derives from the interaction of Al (3s23p1,2P0)+Mn [3d6(5D)4s1,6D]. Combination of the atoms in this excited state leads to a strong σ2 covalent bond via a 3pσAl–4sσMn interaction, which causes this excited electronic state to drop in energy so that it is expected to lie within a few thousand cm−1 of the ground electronic state. Following a discussion of the s...

Electronic spectroscopy and electronic structure of the smallest metal clusters: the diatomic 3D transition metal aluminides

A systematic study of the electronic spectroscopy, electronic structure, and chemical bonding has been initiated for the 3d series of diatomic transition metal aluminides. This report provides a review of the progress to date, with specific emphasis on AlCa, AlV, AlCr, AlMn, AlCo, AlNi, AlCu, and AlZn.