The millimeter-wave spectrum of the SiP radical (X2Πi): Rotational perturbations and hyperfine structure.

The millimeter/submillimeter-wave spectrum of the SiP radical (X2Πi) has been recorded using direct absorption spectroscopy in the frequency range of 151-532 GHz. SiP was synthesized in an AC discharge from the reaction of SiH4 and gas-phase phosphorus, in argon carrier gas. Both spin-orbit ladders were observed. Fifteen rotational transitions were measured originating in the Ω = 3/2 ladder, and twelve in the Ω = 1/2 substate, each exhibiting lambda doubling and, at lower frequencies, hyperfine interactions from the phosphorus nuclear spin of I = 1/2. The lambda-doublets in the Ω = 1/2 levels appeared to be perturbed at higher J, with the f component deviating from the predicted pattern, likely due to interactions with the nearby excited A2Σ+ electronic state, where ΔEΠ-Σ âˆ¼ 430 cm-1. The data were analyzed using a Hund's case aß Hamiltonian and rotational, spin-orbit, lambda-doubling, and hyperfine parameters were determined. A 2Π/2Σ deperturbation analysis was also performed, considering spin-orbit, spin-electronic, and L-uncoupling interactions. Although SiP is clearly not a hydride, the deperturbed parameters derived suggest that the pure precession hypothesis may be useful in assessing the 2Π/2Σ interaction. Interpretation of the Fermi contact term, bF, the spin-dipolar constant, c, and the nuclear spin-orbital parameter, a, indicates that the orbital of the unpaired electron is chiefly pπ in character. The bond length in the v = 0 level was found to be r0 = 2.076 Å, suggestive of a double bond between the silicon and phosphorus atoms.

Trends in alkali metal hydrosulfides: a combined Fourier transform microwave/millimeter-wave spectroscopic study of KSH (X1A').

The pure rotational spectrum of KSH (X(1)A') has been measured using millimeter-wave direct absorption and Fourier transform microwave (FTMW) techniques. This work is the first gas-phase experimental study of this molecule and includes spectroscopy of KSD as well. In the millimeter-wave system, KSH was synthesized in a DC discharge from a mixture of potassium vapor, H2S, and argon; a discharge-assisted laser ablation source, coupled with a supersonic jet expansion, was used to create the species in the FTMW instrument. Five and three rotational transitions in the range 3-57 GHz were recorded with the FTMW experiment for KSH and KSD, respectively, in the K(a) = 0 component; in these data, potassium quadrupole hyperfine structure was observed. Five to six transitions with K(a) = 0-5 were measured in the mm-wave region (260-300 GHz) for the two species. The presence of multiple asymmetry components in the mm-wave spectra indicates that KSH has a bent geometry, in analogy to other alkali hydrosulfides. The data were analyzed with an S-reduced asymmetric top Hamiltonian, and rotational, centrifugal distortion, and potassium electric quadrupole coupling constants were determined for both isotopolgues. The r0 geometry for KSH was calculated to be r(S-H) = 1.357(1) Å, r(K-S) = 2.806(1) Å, and θ(M-S-H) (°) = 95.0 (1). FTMW measurements were also carried out on LiSH and NaSH; metal electric quadrupole coupling constants were determined for comparison with KSH. In addition, ab initio computations of the structures and vibrational frequencies at the CCSD(T)/6-311++G(3df,2pd) and CCSD(T)/aug-cc-pVTZ levels of theory were performed for LiSH, NaSH, and KSH. Overall, experimental and computational data suggest that the metal-ligand bonding in KSH is a combination of electrostatic and covalent forces.

The rotational spectrum of CoF in all three spin-orbit components of the X3Phi i state.

The pure rotational spectrum of cobalt monofluoride in its X (3)Phi(i) electronic state has been measured in the frequency range of 256-651 GHz using direct absorption techniques. CoF was created by reacting cobalt vapor with F(2) in helium at low pressure (25-30 mTorr). All three spin components were identified in the spectrum of this species, two of which exhibited lambda doubling. Each spin component showed hyperfine splittings from both nuclei: an octet pattern arising from the (59)Co spin of I=72, which is further split into doublets due to the (19)F nucleus (I=12). The data were fitted close to experimental precision using an effective Hamiltonian expressed in Hund's case (a) form, and rotational, fine structure, hyperfine, and lambda-doubling parameters were determined. There is evidence that the rotational levels of the highest spin component (3)Phi(2) are perturbed. The r(0) bond length of CoF was estimated from the rotational constant to be 1.738 014(1) A. This value is in good agreement with previous studies but much more accurate. The matrix elements necessary for the complete treatment of Lambda doubling in a Phi state have been derived and are presented for the first time.

High resolution laser excitation spectroscopy of the B2E-X2A1 transitions of calcium and strontium monoborohydride.

High resolution spectra of the B2E-X2A1 transitions of CaBH4 and SrBH4 have been recorded using laser excitation spectroscopy in a laser ablation/molecular jet source. Because of rotational cooling in the molecular jet and nuclear spin statistics, transitions arising from only the K'=1<--K"=0, K'=2<--K"=1, and K'=0<--K"=1 subbands have been observed. For each molecule, an analysis of the data using 2E and 2A1 symmetric top Hamiltonians yielded rotational, spin-orbit, and spin-rotation parameters for the observed states. For both molecules the rotational constants compare well with those calculated for a tridentate borohydride structure. A large reduction in the spin-orbit splitting and in the metal-ligand separation for each molecule indicates an increase in the amount of d atomic orbital character in the first excited 2E states of the monoborohydrides as compared to the monomethyl derivatives. For each molecule no evidence of internal rotation of the BH4- ligand was found. A change in the magnitude and sign of the spin-rotation constant epsilon1 confirms an energy reordering of the first excited 2E and 2A1 states in both CaBH4 and SrBH4 as compared to CaCH3 and SrCH3. The data also suggest that the B2E1/2 rotational energy levels of CaBH4 may be perturbed by a vibronic component of the A2A1 state.

High-resolution laser excitation spectroscopy of the A2E-X2A1 transition of SrCH3.

High-resolution laser excitation spectroscopy has been used to record the A (2)E-X (2)A(1) electronic transition of SrCH(3) in a laser ablation/molecular jet source. Transitions arising from the K(')=1<--K(")=0, K(')=0<--K(")=1, and K(')=2<--K(")=1 subbands have been observed and assigned. The data were modeled with (2)E and (2)A(1) symmetric top Hamiltonian matrices in a Hund's case (a) basis, using a least squares fitting program. Rotational and fine structure parameters for the A (2)E state were determined. A comparison of the spin-orbit energy separation in the A (2)E state to other strontium containing free radicals showed that the Jahn-Teller effect is negligible. The spin-rotation constants for the A (2)E state were calculated using the pure precession model and were found to be in good agreement with the experimentally determined parameters. These calculations suggest that the A (2)E state of SrCH(3) is not entirely of p orbital character. The rotational constants were used to estimate the structural parameters of SrCH(3) in the A (2)E state. The strontium-carbon bond length was found to decrease by approximately 0.006 A, and the hydrogen-carbon-hydrogen bond angle opened by approximately 0.8 degrees compared to the X (2)A(1) state, similar to the geometry changes observed for CaCH(3).

High-resolution spectroscopic investigation of the ~B2A1-- ~X2A1 transitions of CaCH3 and SrCH3.

High-resolution spectra of the ~B(2)A(1)-- ~X(2)A(1) transitions of CaCH(3) and SrCH(3) have been recorded in a molecular jet/laser ablation source using laser excitation spectroscopy. Transitions arising from the K = 0 and 1 sub-bands have been observed for both molecules. An analysis of the data using a (2)A(1) symmetric top Hamiltonian has determined rotational and spin-rotation constants for the ~B(2)A(1) state of each molecule. From the rotational constants, structures have been estimated for both CaCH(3) and SrCH(3). The spin-rotation constant, epsilon(bc) = (epsilon(bb) + epsilon(cc))/2, in the ~B(2)A(1) state for both molecules is in reasonable agreement with the value calculated using the pure precession approximation. For CaCH(3), the K' = 1 levels of the ~B(2)A(1) state exhibit a perturbation that interchanges the energy ordering of the spin-rotation components.

Characterizing the later 3d cyanides: the submillimeter spectrum of CoCN(X 3Phi i).

The pure rotational spectrum of the CoCN radical has been recorded in the frequency range 350-500 GHz using direct absorption techniques. This study is the first spectroscopic observation of this molecule by any experimental technique. Spectra of Co (13)CN have been measured as well. These data indicate that this species is linear in its ground electronic state and has the cyanide, as opposed to the isocyanide, geometry. The ground state term has been assigned as (3)Phi(i), based on the measurement of three spin components (Omega=4, 3, and 2) and in analogy to other isovalent cobalt-bearing species. Hyperfine splittings resulting from the (59)Co nuclear spin of I=7/2 were observed in every transition, each of which exhibited an octet pattern. For the lowest energy spin component, Omega=4, vibrational satellite features were also identified arising from the first quantum of the Co-C (v(1)=1) stretch and the v(2)=1 and v(2)=2 quanta of the bending mode, which were split by Renner-Teller interactions. The ground state measurements of CoCN were analyzed with a case a(beta) Hamiltonian, establishing rotational, fine structure, and hyperfine parameters. The vibrational and Co (13)CN spectra for the Omega=4 component were fit as well. An r(0) structure was also calculated, providing estimates of the Co-C and C-N bond distances, based on the Omega=4 transitions. CoCN is the fourth molecule in the 3d transition metal series to exhibit the linear cyanide structure, along with the Zn, Cu, and Ni analogs. The preference for this geometry, as opposed to the isocyanide form, may indicate a greater degree of covalent bonding in these species.

First synthesis and structural determination of a monomeric, unsolvated lithium amide, LiNH(2).

Alkali metal amides typically aggregate in solution and the solid phase, and even in the gas phase. In addition, even in the few known monomeric structures, the coordination number of the alkali metal is raised by binding of Lewis-basic solvent molecules, with concomitant changes in structure. In contrast, the simplest lithium amide LiNH(2) has never been made in a monomeric form, even though its structure has been theoretically predicted several times. Here, the first experimental structural data for a monomeric, unsolvated lithium amide are determined using a combination of gas-phase synthesis and millimeter/submillimeter-wave spectroscopy. All data point to a planar structure for LiNH(2). The r(o) structure of LiNH(2) has a Li-N distance of 1.736(3) A, an N-H distance of 1.022(3) A, and a H-N-H angle of 106.9(1) degrees. These results are compared with theoretical predictions for LiNH(2), and experimental data for oligomeric, solid-phase samples, which could not resolve the question of whether LiNH(2) is planar or not. In addition, comparisons are made with revised gas-phase and solid-phase data and calculated structures of NaNH(2).

Inbreeding, outbreeding, and heterosis in the yellow pitcher plant, Sarracenia flava (Sarraceniaceae), in Virginia.

The yellow pitcher plant, Sarracenia flava, is an insectivorous plant restricted to fire-maintained wetland ecosystems in southeastern Virginia. Only four natural sites remain in the state totaling fewer than 100 clumps. Plants from sites located in Dinwiddie, Greensville, Prince George, Sussex counties, and the city of Suffolk were tested for the effects of self-pollination, intrasite outcrossing, and intersite outcrossing on offspring quantity (total seed number and total seed mass) and offspring quality (avarage seed mass, germination, and growth).Self-pollination resulted in significantly lower offspring quantity and quality. Total seed number and total seed mass for self-pollinated capsules were approximately one-fourth that of outcrossed capsules. Germination, survivorship, and growth over 5 yr were also significantly lower for offspring from self-pollinated capsules. Together, these results suggest strong inbreeding depression in this species.Relative to offspring from intrasite crosses, offspring from intersite crosses were significantly larger after 5 yr of growth. This suggests that restoration efforts for Virginia S. flava will be most successful when plants from multiple sites are used.

Proportion of unmarried siblings of homosexual and non homosexual gender-dysphoric patients.

Among the siblings of homosexuals, a lack of sexual and romantic interest in women may be independent of erotic feelings for men. This study investigated the sexual histories of siblings of gender-dysphoric outpatients. The patients were classified into three groups: non homosexual males, homosexual males and homosexual females. Their siblings consisted of 301 brothers and 284 sisters over the age of 25. Logistic regression showed that the brothers of the homosexual male patients were significantly less likely to have been married, either legally or common-law, than the brothers of the other gender-dysphoric groups, even with age and relative birth order taken into account. This finding suggests that the low propensity for long term heterosexual relationships seen in homosexual male gender-dysphoric patients also tends to appear in their brothers.

Sibship size, sibling sex ratio, birth order, and parental age in homosexual and nonhomosexual gender dysphorics.

This study investigated whether demographic variables previously reported to differentiate ordinary homosexuals from heterosexuals also differentiate gender-dysphoric homosexuals from gender-dysphoric persons with other sexual orientations. Subjects were outpatients aged 16 and older who were referred by physicians to a specialty clinic for the assessment of gender identity disorders. The subjects were divided into three groups: 204 homosexual women, 193 homosexual men, and 273 nonhomosexual men; the last category included men sexually attracted to females, to both sexes, and to neither sex. Demographic data on patients' families of origin were extracted from their clinical charts and from structured interview protocols. A multiple-range test at the .05 level showed that the homosexual men had significantly more siblings than the homosexual women, who, in turn, had significantly more siblings than the nonhomosexual men. The sibling sex ratio of the homosexual men, 131 brothers per 100 sisters, was significantly higher than the sex ratio of live births for the population as a whole (106 men per 100 women; p = .01); the sibling sex ratios of the other groups did not differ from the expected value. The homosexual men had a significantly later birth order than the nonhomosexual men (p = .004); the homosexual women, who fell in between, did not differ significantly from either male group. There were no between-groups differences in paternal or maternal age at the time of the subject's birth. The results concerning sibling sex ratio and birth order are consistent with previous findings for homosexual men.