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The effects of near ultraviolet (UV) radiation on water solutions of tyrosine and glycine-tyrosine are investigated using a broadband xenon lamp in the region 200–800 nm. These experiments form a contribution in the laboratory simulation of the solar irradiation on the building blocks of life with regard to the origin of life. Results are presented showing the photodecomposition of tyrosine and glycine-tyrosine, at different concentrations, against UV doses. The analysis of the irradiated solutions is carried out by spectroscopic and analytical techniques. The findings of our laboratory simulations are used to constrain the early stages of the life emerging process.

The effects of near ultraviolet (UV) irradiation on water solutions of phenylalanine and tryptophan have been investigated using a broad-band xenon lamp in the region 200–800 nm. This is a step in the laboratory simulation of the effects of Solar radiation on the building blocks of life, specifically α-amino acids, with regards to the origin of life. Results are presented showing the photodegradation of phenylalanine and tryptophan against different UV doses. Some of the degradation products are still protein amino acids. An analysis of the irradiated solutions is carried out by spectroscopic and analytic techniques. The laboratory simulations are discussed in the wake of a life emerging scenario on the primitive Earth.

The molecular environment of the young cluster of Class 0 young stellar objects (YSOs) located in the globule CB34 has been investigated through a multiline millimetre survey. The CO, 1 3 CO, C 1 8 O and CS emissions showthat the present star-forming process is concentrated into three molecular clumps with the size of ∼0.25 pc, which are embedded in a cool more extended gas. The spatial distribution of the high-velocity emission reveals the occurrence of multiple outflows which are associated with the brightest YSOs. The interaction of the outflows with the molecular clumps has been studied by using the abundances of products of shocked chemistry such as SiO and SO. The abundances of these molecules at the high velocities of the outflows can be used to further specify, with respect to the continuum results, the characteristics of the Class 0 YSOs. In particular, one of the YSOs which does not show the presence of SiO and SO at high velocities is thought to be in a more evolved phase where most of the molecules produced at high velocities in the shocked regions have been already destroyed.

The globule CB 34, which harbours a cluster of class 0 young stellar object (YSO) protostars, has been investigated through a multiline SO and SiO survey at millimetre wavelengths. The SO data reveal that the globule consists of three quiescent high-density (∼105 cm−3) clumps, labelled A, B and C, with sizes of ∼0.2–0.3 pc. The SiO data provide evidence for high-velocity gas across the globule. Most likely, the high-velocity gas is distributed in three distinct high-velocity outflows associated with the YSOs in each of the three clumps. High-velocity SO features have been detected only towards the two brightest SiO outflows. These broad SO components exhibit spatial and spectral distributions which are consistent with those of the SiO emission, so they can also be used as tracers of the outflows. The comparison between the spatial and spectral properties of the SO and SiO emissions in the three clumps suggests different evolutionary stages for the embedded YSOs. In particular, the YSO associated with clump C exhibits some peculiarities, namely smaller SiO linewidths, lower SiO column densities, a lack of extended SiO structure and of SO wings, and the presence of a SO spatial distribution which is displaced with respect to the location of the YSO. This behaviour is well explained if the SiO and SO molecules which were produced at high velocities in the shocked region have been destroyed or slowed down because of the interaction with the ambient medium, and the chemistry is dominated again by low-temperature reactions. Thus our observations strongly suggest that the YSO in clump C is in a more evolved phase than the other members of the cluster.

The highly sensitive method of radio-frequency-infrared double resonance inside a CO2 laser is applied to study collision-induced transitions in CH3I in a four-level double resonance scheme. Pure nuclear quadrupole resonances are observed as the result of collision population transfer between different rotational levels. The intensity ratios of the collision-induced dips to the corresponding three-level double resonance signals are measured for a number of transitions in the ground and excited vibrational states. Collision selection rules in the pure gas and in mixtures with polar and non-polar gases are discussed.

A sample of 14 small Bok globules and of eight Herbig Ae/Be stars has been observed in the molecular rotational lines of HCO+, HCN, HNC, N2H+, and C2H at 3 mm wavelength. The observational results have been used together with a pseudo-time-dependent chemical model to study the evolution of a molecular cloud toward the formation of a low-mass star. The new chemical and physical scenario that is inferred from the molecular line data is discussed in relation with the existing literature data obtained from infrared to far-infrared data.

The rotational spectra of H 2 13 COH + and D 2 COD + were observed in the 110–224 GHz frequency region using a magnetically confined negative glow discharge as ion production source. Analysis of the spectra allowed determination of the ground state rotational and quartic centrifugal distortion constants. These new data, together with those of Dore et al. [ Chem. Phys. Lett. 244, 145 (1995)] concerning H 2 COH + , allow an estimate of the molecular structure of protonated formaldehyde.

Thirteen ground state rotational lines of protonated formaldehyde, H 2 COH + , were measured using a magnetically confined negative glow discharge as a production source. These new measurements together with those of Chomiak et al. [Can. J. Phys. 72 (1994) 1078] have allowed a refinement of the rotational parameters. The astrophysical aspects of previous and future searches of this ion are outlined.

A number of pure quadrupole resonances in the ground and v 4 = 1 states of AsH 3 have been measured using the radiofrequency-infrared double-resonance technique in a CO 2 laser cavity. The ground stale resonances were titled together with all available radiofrequency and microwave data using the standard treatment. Strong vibration-rotation interactions between the v 2 = 1 and v 4 = 1 states affect the observed spectrum in the v 4 = 1 state. The Hamiltonian model by Aliev and Hougen ( J. Mol. Spectrosc. 106, 110-123 (1984)) has been used, in the form of a computer program. to describe within the experimental uncertainties the new measurements in a combined analysis with all known experimental data in the v 2 = 1 and v 4 = 1 states.

The infrared spectra of the band of the 2Π–2Π asymmetric hydrogen stretching vibration in the three isotopic acetylene ions C2H2+ (ν3), 13C2H2+ (ν3), and DCCH+ (ν1) have been observed and analyzed. The high resolution infrared spectra were recorded using a difference‐frequency laser spectrometer as the tunable coherent infrared source probing an ac glow discharge. Velocity modulation, noise subtraction, and unidirectional multipassing of the infrared beam through the discharge cell provided high sensitivity. C2H2+ was produced in a gas mixture of H2, He, and either CH4 or C2H2, with a total pressure of ≊7 Torr in multiple‐inlet–outlet air‐, water‐, and liquid‐nitrogen‐cooled discharge tubes; C2H2 freezing precluded its use in liquid‐N2‐cooled discharges. Complicated by a strong perturbation whose maximum occurred at N’=15 for F1 and N’=14 for F2, the assignment of the spectrum of normal C2H2+ was made possible by (1) fortuitous discharge conditions which provided unambiguous discrimination of C2H2+ lines ...

The rotational spectra of the four monosubstituted isotopomers of protonated cyanogen HN13CCN+, HNC13CN+, H15NCCN+, and HNCC15N+, in the ground vibrational state have been investigated in the spectral region from 130–270 GHz, using a negative glow discharge production method. From the moments of inertia of the five monosubstituted species, including the DNCCN+ isotopomer [G. Cazzoli et al., Chem. Phys. Lett. 194, 297 (1992)] and of the parent species HNCCN+ [T. Amano and F. Scappini, J. Chem. Phys. 95, 2280 (1991)], the complete rs structure has been obtained. The alchemy of the ion production has been further improved compared to the previous works.

The millimeter-wave spectrum of DNCCN + has been observed and analyzed. The values of the rotational constants are B 0 =4158.32201(49) MHz and D 0 =0.45089(19) kHz.

The two isotopic forms of stibine, 121 SbH 3 and 123 SbH 3 , have been spectroscopically studied with high resolution. Pure quadrupole resonances both in the ground and in the v 4 = 1 states have been observed using the infrared-radiofrequency double resonance technique in a CO 2 laser cavity. Characteristic hyperfine patterns resulting from direct l -type doubling transitions in the v 4 = 1 state have been measured by microwave spectroscopy. The hyperfine pattern in the ground state is reproduced following the standard treatment. Strong vibration-rotation interactions between the v 2 = 1 and v 4 = 1 states affect the observed spectrum in the v 4 = 1 state. A refined treatment of the vibration-rotation interactions between the hyperfine levels in this state was necessary in order to adequately analyze the experimental data. Quadrupole interaction parameters for a degenerate state of a symmetric-top molecule have been determined for the first time.

The frequency of seven rovibrational transitions in the ν3 band, Q branch of 188OsO4 have been measured with high accuracy. The spectrometer used consists of two CO2 lasers [∼3 W on the 10R(0)], the first of which is stabilized on the 4.3 μm fluorescence Lamb dip of the CO2 and the second on the saturated absorption dip of the rovibrational transitions of 188OsO4. The OsO4 transition frequencies are obtained combining the known frequency of the first laser with the measured frequency of the beat note between the two laser beams. For the assignment of the transitions the recent Fourier transform analysis by Bobin et al. [J. Mol. Spectrosc. 122, 229 (1987)] was used. The access to the 10R(0) laser line has made it possible to investigate, for the first time, the Q branch of the ν3 band of OsO4 in a sub‐Doppler regime. Furthermore, the tetrahedral fine structure in the ground and in the ν3 state has been analyzed using the infrared–radio frequency double resonance technique. The tetrahedral splitting constan...

The highly sensitive method of radio‐frequency–infrared double resonance spectroscopy inside the cavity of a CO2 laser has been applied to the study of collision‐induced transitions of CH379Br and CH381Br in the four level scheme. Various types of radio‐frequency transitions corresponding to A1–A2 and pure quadropole resonances were observed as a result of collision population transfer between different rotational levels. Thus, collision‐induced dips have been measured in the pure gas and in mixtures with polar carbonyl sulfide (OCS) and nonpolar (He, Ar) foreign gases. Clamping experiments were also done, using a second radiation in a six level triple resonance configuration to investigate collision selection rules. The intensity ratios of the collision‐induced dips to the corresponding three level double resonance signals were measured for a number of transitions in the ground and in excited vibrational states. Collision selection rules in the pure gas and in mixtures with polar and nonpolar foreign gas...

The effects of ultraviolet (UV) irradiation on water solutions of tyrosine (HO—C6H4—CH2—CHNH2—COOH) have been investigated using a Xe lamp in the region 200–800 nm. This is a step in laboratory simulation towards reproducing the action of the Solar radiation on the building blocks of life, specifically α-amino acids, in the primitive Earth anoxic conditions. Results are presented showing the photostability of tyrosine against different UV doses. Degradation products partly maintain life building capability and partly do not. A tendency towards structure complexification was observed. The analysis of the irradiated tyrosine solutions was conducted using various spectroscopic and analytic techniques. The laboratory results are discussed in the light of a primordial life-emerging scenario.

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The ground‐state rotational spectrum of protonated cyanogen, HNCCN+, has been identified following the infrared detection by Warner and Amano [J. Mol. Spectrosc. 145, 66 (1991)], using a hollow cathode discharge as production source. The rotational and centrifugal distortion constants have been determined to be 4438.010 13(71) MHz and 0.529 95(24) kHz, respectively.

The detection of a new water maser source on the 6 16 → 5 23 transition in the Bok globule LBN 594 is presented. Besides the main feature, a number of velocity components were detected. Spectra taken within a few days interval suggest possible maser variability. Maser emission was also confirmed for two Ae/Be Herbig stars. Upper limits (3σ) are given for the 79 observed globules and 12 Herbig stars

We have studied a sample of seven dark clouds (Bok globules) and eight Hergib Ae/Be stars in the J=1 → 0 transition of HCO+, H13CO+, HCN, and H13CN. The most abundant isotopomers were found in almost all the sources (detection rate 70–90%).From the derived physical parameters and column densities it seems that a quite similar scenario applies for the dark clouds and the gas around the Herbig stars. These similarities, together with the already known features from literature, suggest that the presently studied globules are likely to be sites of low‐mass star formation.

This paper is intended as part of a more extensive molecular line survey in star forming regions along the evolutionary track of a collapsing cloud toward a young stellar object. We have studied a sample of seven small dark clouds (Bok globules) and eight Herbig Ae/Be stars in the J=1->0 transition of HCO$^{+}$, H$^{13}$CO$^{+}$, HCN and H$^{13}$CN. The choice of these molecules is determined by the simple chemistry and the predicted high abundance of the reactants leading to their formation. The isotopically substituted species (isotopomers), H$^{13}$CO$^{+}$ and H$^{13}$CN, were observed in order to determine, whenever possible, the optical thickness of the main species. The most abundant isotopomers were found in almost all the sources (detection rate 70-90\%). Those sources which exhibited the strongest signals were also searched for the $^{13}$C isotopomers. H$^{13}$CO$^{+}$ was found in one dark cloud and around three Herbig Ae/Be stars, while H$^{13}$CN around only one star. The column densities for each species and the physical conditions of the objects were derived whenever the observational data allowed it., 16 pages plus 6 figures available in hardcopy from ggcpalumbo@alma02.cineca.it LaTEX ver. 2.09, BAP 11-1993-036-DDA

The high-resolution microwave spectrum of the axial conformer of cyclohexyl chloride has been assigned for both the Cl(35) and Cl(37) isotopic species, in natural abundance. Moreover, the high-resolution microwave spectrum of the equatorial conformer, previously assigned in the ground state [ Chem. Phys. Lett. 21 , 592–594 (1973)], has been further investigated. Several low-energy vibrational satellites have been studied for the Cl(35) isotopic species of both the axial and the equatorial isomers. The ground state centrifugal distortion constants for both the isotopic species of the two rotamers, and the quadrupole coupling constants of Cl(35) and Cl(37) axial isomer and of Cl(37) equatorial isomer (not reported previously) have been determined. From line relative intensity measurements the energy difference between the two conformers has been calculated to be 0.51 ± 0.15 kcal/mol, the equatorial isomer being more stable. In the same way, the vibrational energies of the investigated vibrational satellites have been computed. A structural model for axial cyclohexyl chloride is proposed on the basis of the available experimental data.

The microwave spectra of cyclohexyl bromide and cyclohexyl iodide have been investigated in the gas phase between 8 and 40 GHz. While for cyclohexyl bromide only low resolution spectra have been recorded, for cyclohexyl iodide high resolution spectra of both the equatorial and the axial isomer have been analyzed. The energy difference between the axial and the equatorial form is Δ G ° = 0.8 ± 0.4 kcal/mole and Δ E 0,0 = 0.54 ± 0.15 kcal/mole in C 6 H 11 Br and C 6 H 11 I, respectively, the equatorial forms being more stable. Iodine nuclear quadrupole coupling constants for equatorial and axial C 6 H 11 I have been obtained. The present analysis contributes to the microwave investigation of the cyclohexyl halides.

The high-resolution microwave spectra of the79Br and81Br isotopic species of cyclohexyl bromide, C6H11Br, have been assigned for the equatorial and axial isomers, respectively. The ground-state energy of the axial isomer is 0.72 ± 0.30 kcal/mole higher than that of the equatorial one. The quadrupole coupling constants have been obtained for the equatorial and axial ground states of both the isotopes. Several vibrational excited states of the equatorial and axial conformers (79Br) have also been analyzed.

Electric nuclear quadrupole hyperfine structure arising from a quadrupolar nucleus at the center of tetrahedral molecules, such as 189OsO4, is symmetry forbidden. However, through vibration–rotation distortion a small nuclear quadrupole coupling is induced. The hyperfine structure due to the vibrationally induced eqQ has been measured for a number of P‐ and R‐branch transitions in the ν3 fundamental of 189OsO4, by using inverse Lamb dip spectroscopy. Microwave modulation sidebands of CO2 laser lines have been used as the tunable infrared radiation. From the analysis of the observed hyperfine structure patterns, the values of the scalar and tensor coupling constants have been determined to be χVs=−4.103±0.048 MHz and χVt=−3.090±0.059 MHz.

An analysis of the microwave spectrum of HNSO and DNSO has been performed, extended with respect to a preceding work, in order to determine the first-order P 1 centrifugal distortion constants. From the b-type spectrum of DNSO, not previously assigned, the rotational constant A of this species has been evaluated. The H–N bond r s distance has been calculated to be 1.0272±0.0001 A.

The microwave spectra of 1,1′-dimethyl-2,2′-dicyanoethylene and 1,1′-dimethyl-2,2′-dicyanoethylene-d6 have been recorded in the frequency region 18–40 GHz. The measured ground state lines have been fitted to a semi-rigid rotor model. From the resulting six moments of inertia some structural information has been obtained.

The infrared spectrum of gaseous acetyl cyanide, CH3COCN, has been recorded from 90 - 3200 cm-1. The Raman spectrum of the liquid phase has been measured between 100 and 500 cm-1. The eighteen fundamental vibrations have been assigned, mainly on the basis of the infrared band contours, and a normal coordinate analysis has been made.

Three methods are discussed to determine the electric dipole moment of asymmetric top molecules in those cases where the conventional second order Stark pattern is difficult to identify, because of spectral complexity. The methods are applied to a test molecule and to a number of molecules whose dipole moments were not previously determined.

The rotational spectrum of lactonitrile, CH3CH(OH)CN, has been reinvestigated. The analysis has been extended to the CH3CH(OD)CN species and to several excited states of the hydroxyl and methyl internal rotations. The molecule exhibits two conformers with the hydroxyl hydrogen gauche with respect to the cyano group. The conformer A with the hydroxyl hydrogen adjacent to the methinic hydrogen is 118±30 cm−1 (75±30 cm−1 for the OD species) more stable than the conformer B with the hydroxyl hydrogen adjacent to the methyl group. The barrier height to the interconversion is about 400 cm−1. Rotational A–E splittings due to methyl internal rotation have been observed in the first excited state of both conformers, yielding effective V3 barriers of 3.7 kcal/mol for conformer A and 4.3 kcal/mol for conformer B. By using a one‐dimensional flexible model treatment the potential function and the structural relaxation associated with the OH torsion have been determined from the level spacings and the variations of the...

The two isotopic species CH 2 DCOOH and CH 2 DCOOD of acetic acid have been investigated with microwave spectroscopy in order to determine the equilibrium configuration of the methyl group, which was found to be eclipsed with respect to the carbonyl group. Centrifugal distortion constants free from internal rotation effects have been determined. A r s structure for the four hydrogens and a partial r 0 structure for the whole molecule are given.

The microwave ground state spectrum of cis propionyl fluoride has been investigated expanding, with respect to a previous study, the range of the quantum numbers of the transitions, J up to 40 and K up to 18. At low K the spectrum resembles that of an asymmetric rigid rotor, except in a number of cases where the lines are split into A, E doublets. At intermediate and high K the mixing of the if-doublet rigid rotor wave functions makes forbidden transitions appear. The results of the analysis of the methyl top internal rotation ground state splittings are: V3 = 2350 ± 11 cal/mole, ≮ (i, a) = 32.7° ±2.0°, and Iα = 3.18 ± 0.03 uÅ2.

A reinvestigation of the microwave spectrum of N-methyl-p-fluoroaniline shows this molecule to have low lying excited vibrational states associated with the inversion and torsion of the HNCH3 group similar to N-methylaniline. The experimental data indicate a greater tendency towards a planar configuration at the nitrogen atom and a lower barrier to inversion compared to p-fluoroaniline.

The analysis of the microwave spectra of some excited states of the skeletal torsion in both antiperiplanar and synclinal forms of normal propyl fluoride has been extended in order to obtain the splittings (Δ0=EE -EA ) due to the methyl group internal rotation. The results have been used, together with the experimental data already available, to obtain information on the structural relaxation upon torsional excitation and conformation exchange, and to evaluate a simple set of potential energy parameters for the two torsions by applying one- and two-dimensional flexible models.

A tunable color center laser has been used as the infrared radiation source for infrared-radio-frequency double resonance spectroscopy. The A1–A2 splitting (J, K = 1, l = 1 and J, K = 2, l = −1) in the ν4 vibrational state of CH3F has been studied. This technique has also been used to measure the electric dipole moment for the ν4 state, which has been determined to be 1.8332(23) D.

The Stark effect of rotational and torsio-rotational transitions of propargyl mercaptan has been analyzed. Assuming a dependence of the dipole moment components on the internal rotation angle of the type: μ a = μ a 0 + μ a (1) cos α , μ b = μ b 0 + μ b (1) cos α , and μ c = μ c (1) sin α , the following values of the determinable quantities were obtained: μ a eff = 0.718 ± 0.003 D , μ b eff = 0.495 ± 0.010 D , and μ c (1) = 0.809 ± 0.015 D . The SH bond moment was also evaluated from μ c (1) and compared with the SH bond moment of similar molecules.

The rotational Zeeman effect of FClCO is reported. The Chlorine nuclear gI-factor, the molecular g-factors, gaa , gbb , and gcc , and the magnetic susceptibility anisotropics, (2 χaa- χbb - χcc) mole and (2 χbb - χcc - χaa) mole, are obtained from the spectrum. Some derivative molecular quantities are calculated.

Low resolution microwave spectra of four isotopic species and high resolution microwave spectra of two isotopic species of N-methyl-p-fluoroaniline have been recorded. The rotational constants obtained by each method were used separately for fitting the structure and the results were compared. The N-methyl-p-fluoroaniline molecule is found to be more nearly planar than aniline and p-fluoroaniline, the out-of-plane angle of the HNCH3 group being φ = 18° ± 3°.

The microwave spectrum of C4O2Cl2 (1,2-dichlorocyclobuten-3,4-dione) has been investigated for both the C4O235Cl2 and the C4O235Cl37Cl isotopomers. The spectrum of the latter has been studied in greater detail because a number of μb rotational transitions were measured with the radiofrequency-microwave double-resonance technique by radiofrequency pumping of some K−1 doublets. This pumping has been made possible since a small μa dipole moment component appears owing to the asymmetric isotopic substitution.

Application de cette methode en vue de determiner les constantes de decomposition dans l'etat (Z t ) de OsO 4

The rotational spectrum of N-methylpyrrolidine has been measured in the ground state and eight excited vibrational states. The molecule shows a bent configuration with the nitrogen atom out of the plane containing the carbon atoms and with the methyl group in the equatorial position. From the analysis of the A-E rotational splittings in the first excited state of the methyl torsion, the corresponding barrier has been calculated to be 3860 ± 50 cal/mole. The spacings between the levels of the ring puckering are in accordance with the relatively high barrier to pseudorotation previously obtained by ab initio calculations. Finally, the 14N quadrupole coupling constants and the electric dipole moment have been determined.

The ground state microwave rotational spectra of the axial and equatorial chair forms of ethynyl-cyclohexane are investigated in the frequency region 8–26.5 GHz. The spectrum of the first vibrationally excited state of the e-conformer is also assigned and intensity measurements locate this state at 130 ± 30 cm−1. Using the ground state rotational constants obtained for the two isomers, a least-squares structural analysis is performed.

The rotation-torsion-vibration interaction in acetyl cyanide, CH3COCN, has been studied in the rotational spectra of the first excited state of the methyl torsion and of the CCN-in-plane bending. A model with two internal degrees of freedom has been used to account for the A-E rotational splittings in the ground state and in the two excited states simultaneously. The constants in the Fourier expansion of the potential hindering the methyl torsion are determined. The results are compared with those obtained in a previous work from the A-E rotational splittings of the ground state only, using a model with one degree of freedom. Group theoretical considerations are made upon the Hamiltonian used in the present analysis.

The microwave spectrum of the deuterated propargyl mercaptan was recorded and measurements in the torsional levels 0± and 1± are reported. The internal rotation analysis is carried further using the new data obtained and a more specific Hamiltonian. With the mean values of the rotational constants for the two isotopic species in the states 0±, a r0-structure is proposed.

The microwave spectra of acetyl cyanide, CH3COCN, in the ground and in the two lowest excited states have been investigated. The rotational constants and the quadrupole coupling constants have been evaluated for all these states. The internal rotation parameters have been refined with respect to previous works. Evidence for a rotation-torsion -vibration interaction has been found in the spectra of the excited states.