Resonant two-photon ionization spectroscopy of jet-cooled Pt?

Journal ArticleThe gas phase optical spectrum of jet-cooled Pt? has been investigated over the range of 11 300 to 26 300 cm -1 using resonant two-photon ionization spectroscopy in combination with time-of-flight mass spectrometry. Numerous vibronic bands are observed. Analysis of the data gives the location of some 26 excited electronic states, which are characterized by the frequencies of their origin bands, vibrational frequencies, and anharmonicities. Variation of the second color in a two-color resonant two-photon ionization scheme has determined the ionization threshold of Pt? to be 8.68 ?0.02 eV. The observation of the onset of predissociation, characterized by a sharp drop in excited state lifetime, places the dissociation energy of Pt? at 3.14?0.02 eV. In combination with the Pt atomic ionization potential of 8.8?0.2 eV, these results give the bond strength of Pt?+ as D0(Pt--Pt+) = 3.26 ? 0.24 eV. The strength of the chemical bond in Pt?, as compared to Au?, demonstrates that there are significant 5d contributions to the chemical bonding in Pt?

Spectroscopy and electronic structure of jet-cooled Al?

Journal ArticleResonant two-photon ionization spectroscopy has been used to study the jet-cooled Al? molecule. The ground state has been conclusively demonstrated to be of 3IIu symmetry, deriving from the ???rr?u electronic configuration. High resolution studies have established the bond length of the X?IIu state as re (X?IIu) = 2.701 ? 0.002 ?. The third-law estimate of the Al? bond strength has been reevaluated using the observed and calculated properties of the low-lying electronic states to give Do (Al?) = 1.34 ? 0.06 eV. In addition to the previously reported E 2 ??-g 2 ?X?IIu and F 3??-g ?X3IIu band systems, the E' 3?IIg ?X?IIu, F"-X, F'-X, G ?IIg ?X?IIu, H' ??-g ?X?IIU, and H??g ?X?IIu band systems have been observed for the first time. Bands of the G-X, H '-X, and H-X systems have been rotationally resolved and analyzed, providing rotational constants and electronic state symmetries for the upper states of these systems. A discussion of all of the experimentally known states of Al2 is presented, along with comparisons to previous experimental and theoretical work

Rydberg and pulsed field ionization-zero electron kinetic energy spectra of YO

Journal ArticleA spectroscopic study of the Rydberg states of YO accessed from particular rotational levels of the A 2II1/2, v=0 state has been combined with a pulsed field ionization, zero electron kinetic energy (PFI-ZEKE) investigation. The results provide accurate values of the ionization energy of YO, ionization energy I.E.(YO)=49 304.316(31) cm-1 [6.112 958](4) eV], and of the rotational constant (and bond length) of the YO+ cation in its X 1?+, v=0 ground state, B0+=0.4078(3) cm21 [r0=1.7463(6) ?]. The improved value of I.E.(YO) combined with the known ionization energy of atomic yttrium then leads to the result D0 0 (Y+-O)2D0 0 (Y2O=0.1041?0.0001 eV. Combining this result with the value of D0 0 (Y+-O) obtained from guided ion beam mass spectrometry yields an improved value of D0 0 (Y+O)=7.14?0.18 eV. The PFI-ZEKE spectra display an interesting channel-coupling effect so that all rotational levels with J+?J'(A)+0.5 are observed with high intensity, where J+ is the angular momentum of the YO+ cation that is produced and J'(A) is the angular momentum of the A 2II1/2 state that is reached when the first photon is absorbed. This is thought to result from the interaction between the dipole moment of the rotating YO+ core and the Rydberg electron, which can induce changes in l and J+ subject to the dipolar coupling matrix element selection rule, ?J+=?1, ?l=?1. The channel-coupling mechanism also appears to induce an inverse autoionization process in which an unbound electron with a low value of l is captured either by its low-J+1 YO+ cation or by a second YO+ cation with the same value of J+. This inverse autoionization process is extremely sensitive to the electron kinetic energy, leading to narrow peaks in the PFI-ZEKE spectrum which are only slightly broader than the laser linewidth employed for this study (0.25 cm-1)

Spectroscopy of diatomic ZrF and ZrCl: 760 ? 555 nm

Journal ArticleThe optical spectrum of diatomic ZrF has been investigated, with transitions recorded in the range from 14 700 to 18 000 cm?1. Many bands have been observed, several of which can be grouped into three band systems. Rotationally resolved investigations are hampered by perturbations that are rampant among the excited states, but three unperturbed bands have revealed that the ground state of ZrF has ?" = 3/2, with a bond length of r"e = 1.854(1) ?. Hot bands originating from v" = 1 provide the ground state vibrational interval, ?G"1/2 = 691.45(2) cm?1 for 90Zr19F. Based on comparisons to ZrCl and ligand-field considerations, the ZrF ground state is assigned as a 2?3/2 level deriving from the 3?2 1?1 configuration, in agreement with a previous study. In addition to the measurements on ZrF, vibronically resolved spectra of ZrCl have been recorded over the 13 000 to 18 000 cm?1 range, and four band systems have been identified

Spectroscopic studies of the jet-cooled aluminum trimer

Journal ArticleGas phase spectroscopic investigations of the jet-cooled aluminum trimer are reported using the technique of resonant two-photon ionization with mass spectrometric detection. A discrete band system in the 5200-6100 ? region is observed, consisting of an extended vibrational progression in a single vibrational mode. In addition, an apparent continuum absorption is observed which gradually grows in toward shorter wavelengths. The apparent continuum exhibits a long lifetime, 24-35 ?s, which is most unusual and indicates that the continuum arises from spectral congestion and not lifetime broadening. At 19 378 cm-1 both the discrete and the continuum absorptions terminate abruptly, indicating the onset of dissociation above this energy. Although it is not certain that dissociation above this energy leads to ground electronic state Al2, this measurement nevertheless places an upper limit on D0( A12-A1) of 2.40 eV

Resonant two-photon ionization spectroscopy of jet-cooled PtSi

Journal ArticleJet-cooled diatomic PtSi, produced in a laser ablation supersonic expansion source, has been spectroscopically investigated between 17 400 and 24 000 cm-1 by resonant two-photon ionization spectroscopy. Two vibrational progressions are observed and identified as the [15.7]?'=1 ?X 1?+ and [18.5]?'=1 ?X 1?+ band systems. Three bands in the former system and six bands in the latter system were rotationally resolved and analyzed, leading to bond lengths of r'e=2.1905(13) ? and r'e=2.2354(3) ? for the [15.7]?'=1 and [18.5]?'=1 states, respectively. The ?"=0 ground state of PtSi is assigned as a 1?+ state, in agreement with previous work and with the assigned ground states of the isovalent NiC, PdC, PtC, and NiSi molecules. The ground state bond length of PtSi is given by r'o=2.0629(2) ?. A Rydberg?Klein?Rees analysis of the ground and excited state potential energy curves is presented, along with a discussion of the chemical bonding and a comparison to the isoelectronic molecule, AlAu. Evidence is presented for a double bond in PtSi, as opposed to a single bond in AlAu

Rotationally resolved spectra of jet-cooled VMo

Journal ArticleThe Author's report the first gas-phase spectroscopic investigation of diatomic vanadium molybdenum (VMo). The molecules were produced by laser ablation of a VMo alloy disk and cooled in a helium supersonic expansion. The jet-cooled VMo molecules were studied using resonant two-photon ionization spectroscopy. The ground state has been demonstrated to be of 2?5/2 symmetry, deriving from the d?2drr4d?3s?2 electronic configuration. Rotational analysis has established the ground state bond length and rotational constant as r0"=1.876 57(23) ? and B0"=0.142 861(35) cm?1, respectively, for 51V98Mo (1? error limits). Transitions to states with ?' =2.5, ?'=3.5, and ?'=1.5 have been recorded and rotationally analyzed. A band system originating at 15 091 cm?1 has been found to exhibit a vibrational progression with ?e' =752.7 cm?1, ?'exe'=12.8 cm?1, and r0'=1.90 ? for 51V98Mo. The measured bond lengths (r0) of V2, VNb, Nb2, Cr2, CrMo, Mo2, VCr, NbCr, and VMo have been used to derive multiple bonding radii for these elements of r(V)=0.8919 ?, r(Nb)=1.0424 ?, r(Cr)=0.8440 ?, and r(Mo)=0.9725 ?. These values reproduce the bond lengths of all nine diatomics to an accuracy of ?0.012 ? or better

Resonant two-photon ionization spectroscopy of jet-cooled tantalum carbide, TaC

Journal ArticleThe optical spectrum of diatomic TaC has been investigated for the first time, with transitions recorded in the range from 17 850 to 20 000 cm?1. Six bands were rotationally resolved and analyzed to obtain ground and excited state parameters, including band origins, upper and lower state rotational constants and bond lengths, Fermi contact parameter bF for the ground state, and lambda doubling parameters for the excited states. The ground state of TaC was found to be X ??+, originating from the 1??2??1?3?1 electronic configuration, in which only the valence orbitals arising from the Ta(5d+6s) and C(2s+2p) orbitals are listed. All of the rotationally resolved and analyzed bands were found to originate from the ground state, giving B"0=0.489 683(83) cm?1, r"0=1.749 01(15) ?, and b"F=0.131 20 (36) cm?1 (1? error limits) for 181Ta 12C. Comparison of the Fermi contact parameter to the atomic value shows that the 3? orbital is approximately 75% Ta 6s in character. The other group 5 transition metal carbides, VC and NbC, have long been known to have 1??2??1rr?1?1, ?? ground states, with low-lying 1??2??1rr?3?1, ??+ excited states. The emergence of a different ground state in TaC, as compared to VC and NbC, is due to the relativistic stabilization of the 6s orbital in Ta. This lowers the energy of the 6s-like 3? orbital in TaC, causing the 1??2??1rr?3?1, 2?+ state to fall below the 1??2??1rr?1??, ?? state

Rotationally resolved spectra of jet-cooled RuSi

Journal ArticleWe report the first gas-phase spectroscopic investigation of diatomic ruthenium silicide (RuSi). The molecules were produced by laser ablation of a Ru disk into a flow of helium carrier gas containing 0.5% SiH4, and were cooled in a supersonic expansion. The RuSi molecules were then studied using resonant two-photon ionization spectroscopy. Investigations conducted in the spectral range from 18 800 to 23 800 cm?1 show a large number of excited vibronic levels that cannot readily be grouped into electronic band systems. The ground state is been demonstrated to be of 3?3 symmetry, deriving from the 2?314?1 electronic configuration. Correcting for the effects of the spin-uncoupling operator, the ground state bond length (r0) is determined to be 2.0921?0.0004 ? (1? error limit). Diatomic RuSi is shown to have strong drr-prr bonds, unlike the isovalent AlCo molecule

Resonant two-photon ionization spectroscopy of BNB

Journal ArticleTriatomic BNB has been produced by laser ablation of a boron nitride rod in a supersonic expansion of helium carrier gas and has been investigated using resonant two-photon ionization spectroscopy in the visible region. The B? 2IIg?X? 2?u + band system has been recorded near 514 nm and is dominated by a strong origin band, which has been rotationally resolved and analyzed. Both the 11B14N11B (64% natural abundance) and the 10B14N11B (32% natural abundance) isotopic modifications have been analyzed, leading to the spectroscopic constants (and their 1 error limits) of B"0(X? 2?u+)=0.466 147(70), B'0(B? 2IIg)=0.467 255(75), and A'0(B? 2IIg)=6.1563(38) cm?1 for 10B14N11B, corresponding to r"B ?N(?X 2?u+)=1.312 47(10) ? and r"B ?N(?B 2IIg)=1.310 92(11) ?. Very similar values are obtained for the more abundant isotopomer, 11B14N11B: B'0(X? 2?u+) =0.444 493(69), B'0(B? 2IIg)=0.445 6069(70), A'0(B? 2IIg)=6.1455(38) cm?1, corresponding to r"B ?N(?X 2?u+)=1.312 41(10) ? and r'b ?N(?B 2IIg)=1.310 77(10) ?. These results are discussed as they relate to Walsh?s rules and are compared to results for related molecules