PGOPHER IN THE CLASSROOM AND THE LABORATORY

textsc{pgopher}footnote{textsc{pgopher}, a Program for Simulating Rotational, Vibrational and Electronic Structure, C. M. Western, University of Bristol, http://pgopher.chm.bris.ac.uk}footnote{textsc{pgopher} version 8.0, C M Western, 2014, University of Bristol Research Data Repository, doi:10.5523/bris.huflggvpcuc1zvliqed497r2} is a general purpose program for simulating and fitting rotational, vibrational and electronic spectra. As it uses a graphical user interface the basic operation is sufficiently straightforward to make it suitable for use in undergraduate practicals and computer based classes. This talk will present two experiments that have been in regular use by Bristol undergraduates for some years based on the analysis of infra-red spectra of cigarette smoke and, for more advanced students, visible and near ultra-violet spectra of a nitrogen discharge and a hydrocarbon flame. For all of these the rotational structure is analysed and used to explore ideas of bonding. The talk will discuss the requirements for the apparatus and the support required. Other ideas for other possible experiments and computer based exercises will also be presented, including a group exercise. The textsc{pgopher} program is open source, and is available for Microsoft Windows, Apple Mac and Linux. It can be freely downloaded from the supporting website http://pgopher.chm.bris.ac.uk. The program does not require any installation process, so can be run on student�s own machines or easily setup on classroom or laboratory computers

Line Strengths of Rovibrational and Rotational Transitions in the X2Π^2\Pi Ground State of OH

A new line list including positions and absolute intensities (in the form of Einstein $A$ values and oscillator strengths) has been produced for the OH ground X\DP\ state rovibrational (Meinel system) and pure rotational transitions. All possible transitions are included with v\primed and v\Dprimed up to 13, and $J$ up to between 9.5 and 59.5, depending on the band. An updated fit to determine molecular constants has been performed, which includes some new rotational data and a simultaneous fitting of all molecular constants. The absolute line intensities are based on a new dipole moment function, which is a combination of two high level ab initio calculations. The calculations show good agreement with an experimental v=1 lifetime, experimental $\mu_\mathrm{v}$ values, and $\Delta$v=2 line intensity ratios from an observed spectrum. To achieve this good agreement, an alteration in the method of converting matrix elements from Hund's case (b) to (a) was made. Partitions sums have been calculated using the new energy levels, for the temperature range 5-6000 K, which extends the previously available (in HITRAN) 70-3000 K range. The resulting absolute intensities have been used to calculate O abundances in the Sun, Arcturus, and two red giants in the Galactic open and globular clusters M67 and M71. Literature data based mainly on [O I] lines are available for the Sun and Arcturus, and excellent agreement is found.Comment: 17 pages, 8 figues. 7 supplementary files: dipole moment functions (OH-X-DMFs.txt), equilibrium constants (OH-X-Equilibrium_Constants.txt), partition function (OH-X-Q_5-6000K.dat), PGOPHER file with molecular constants and transition matric elements (OH-XX.pgo), vibrational Einstein A and f values (OH-XX-Avv_fvv.txt), line list (OH-XX-Line_list.txt), and OH-Transformation_Equation_Extra.doc

Note: Improved line strengths of rovibrational and rotational transitions within the X3Σ− ground state of NH

Recently, a line list including positions and transition strengths was published for the NH X3Σ− rovibrational and rotational transitions. The calculation of the transition strengths requires a conversion of transition matrix elements from Hund’s case (b) to (a). The method of this conversion has recently been improved during other work on the OH X2Π rovibrational transitions, by removing an approximation that was present previously. The adjusted method has been applied to the NH line list, resulting in more accurate transition strengths. An updated line list is presented that contains all possible transitions with v′ and v″ up to 6, and J up to between 25 and 44, depending on the band

Automatic assignment and fitting of spectra with PGOPHER

An open source program for automatically assigning complex, well resolved spectra.</p

Rotational Temperature Modeling of the Swan Δν = 0 Band Sequence in Comet 122P/de Vico

We modeled observations of the C$_2$ $\mathrm{d} ^3\Pi_g - \mathrm{a} ^3\Pi_u$ (Swan) $\Delta \nu = 0$ sequence observed in spectra of comet 122P/de Vico obtained with the 2.7m Harlan J. Smith Telescope and Tull Coude spectrograph of McDonald observatory on 10/03/1995 and 10/04/1995. The data used spanned 4986-5169\AA at R=$\lambda/\Delta\lambda$=60,000. We used the PGOPHER molecular spectra model to generate and fit synthetic spectra with the d$^3\Pi_g$ having one and two rotational temperatures. We found the excited state had a two component rotational temperature, similar to that found for comet Halley. The modeled spectrum was sufficiently high quality that local perturbations were important to include. The large perturbation, b$^3\Sigma_g^-(\nu=10)$, was added to our fits and some new estimates on its molecular constants were found.Comment: This document is the unedited Author's version of a Submitted Work that was subsequently accepted for publication in Journal of Physical Chemistry, Part A:Isolated Molecules, Clusters, Radicals, and Ions; Environmental Chemistry, Geochemistry, and Astrochemistry; New Tools and Methods, copyright American Chemical Society after peer revie

Measurement of the orientation of buffer-gas-cooled, electrostatically-guided ammonia molecules

AbstractThe extent to which the spatial orientation of internally and translationally cold ammonia molecules can be controlled as molecules pass out of a quadrupole guide and through different electric field regions is examined. Ammonia molecules are collisionally cooled in a buffer gas cell, and are subsequently guided by a three-bend electrostatic quadrupole into a detection chamber. The orientation of ammonia molecules is probed using (2+1) resonance-enhanced multiphoton ionisation (REMPI), with the laser polarisation axis aligned both parallel and perpendicular to the time-of-flight axis. Even with the presence of a near-zero field region, the ammonia REMPI spectra indicate some retention of orientation. Monte Carlo simulations propagating the time-dependent Schrödinger equation in a full basis set including the hyperfine interaction enable the orientation of ammonia molecules to be calculated – with respect to both the local field direction and a space-fixed axis – as the molecules pass through different electric field regions. The simulations indicate that the orientation of ∼95% of ammonia molecules in JK=11 could be achieved with the application of a small bias voltage (17V) to the mesh separating the quadrupole and detection regions. Following the recent combination of the buffer gas cell and quadrupole guide apparatus with a linear Paul ion trap, this result could enable one to examine the influence of molecular orientation on ion-molecule reaction dynamics and kinetics

Einstein A Coefficients and Oscillator Strengths for the A 2Π-X2Σ+ (Red) and B 2Σ+-X2Σ+ (Violet) Systems and Rovibrational Transitions in the X2Σ+ State of CN

Line strengths have been calculated in the form of Einstein A coefficients and f-values for a large number of bands of the A 2Π-X 2Σ+ and B 2Σ+-X 2Σ+ systems and rovibrational transitions within the X 2Σ+ state of CN using Western\u27s PGOPHER program. The J dependence of the transition dipole moment matrix elements (the Herman-Wallis effect) has been taken into account. Rydberg-Klein-Rees potential energy functions for the A 2Π, B 2Σ+ , and X 2Σ+ states were computed using spectroscopic constants from the A 2Π-X 2Σ+ and B 2Σ+-X 2Σ+ transitions. New electronic transition dipole moment functions for these systems and a dipole moment function for the X 2Σ+ state were generated from high level ab initio calculations and have been used in Le Roy\u27s LEVEL program to produce transition dipole moment matrix elements (including their J dependence) for a large number of vibrational bands. The program PGOPHER was used to calculate Einstein A coefficients, and a line list was generated containing the observed and calculated wavenumbers, Einstein A coefficients and f-values for 290 bands of the A 2Π-X 2Σ + transition with v′ = 0-22, v″ = 0-15, 250 bands of the B 2Σ+-X 2Σ+ transition with v′ = 0-15, v″ = 0-15 and 120 bands of the rovibrational transitions within the X 2Σ+ state with v = 0-15. The Einstein A coefficients have been used to compute radiative lifetimes of several vibrational levels of the A 2Π and B 2Σ + states and the values compared with those available from previous experimental and theoretical studies. © 2014. The American Astronomical Society

First high-resolution infrared spectra of 2–13C-propane:Analyses of the ν26 (B2) c-type and ν9 (A1) b-type bands

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